BOSTON - Two bombs exploded in the crowded streets near the finish line of the Boston Marathon on Monday, killing at least three people and injuring more than 140 in a bloody scene of shattered glass and severed limbs that raised alarms that terrorists might have struck again in the U.S.
A White House official speaking on condition of anonymity because the investigation was still unfolding said the attack was being treated as an act of terrorism.
President Barack Obama vowed that those responsible will "feel the full weight of justice."
As many as two unexploded bombs were also found near the end of the 26.2-mile course as part of what appeared to be a well-coordinated attack, but they were safely disarmed, according to a senior U.S. intelligence official, who also spoke on condition of anonymity because of the continuing investigation.
The fiery twin blasts took place about 10 seconds and about 100 yards apart, knocking spectators and at least one runner off their feet, shattering windows and sending dense plumes of smoke rising over the street and through the fluttering national flags lining the route. Blood stained the pavement, and huge shards were missing from window panes as high as three stories.
"They just started bringing people in with no limbs," said runner Tim Davey of Richmond, Va. He said he and his wife, Lisa, tried to shield their children's eyes from the gruesome scene inside a medical tent that had been set up to care for fatigued runners, but "they saw a lot."
"They just kept filling up with more and more casualties," Lisa Davey said. "Most everybody was conscious. They were very dazed."
As the FBI took charge of the investigation, authorities shed no light on a motive or who may have carried out the bombings, and police said they had no suspects in custody. Officials in Washington said there was no immediate claim of responsibility.
Police said three people were killed. An 8-year-old boy was among the dead, according to a person who talked to a friend of the family and spoke on condition of anonymity.
Hospitals reported at least 144 people injured, at least 17 of them critically. The victims' injuries included broken bones, shrapnel wounds and ruptured eardrums.
At Massachusetts General Hospital, Alisdair Conn, chief of emergency services, said: "This is something I've never seen in my 25 years here ... this amount of carnage in the civilian population. This is what we expect from war."
Some 23,000 runners took part in the race, one of the world's oldest and most prestigious marathons.
One of Boston's biggest annual events, the race winds up near Copley Square, not far from the landmark Prudential Center and the Boston Public Library. It is held on Patriots Day, which commemorates the first battles of the American Revolution, at Concord and Lexington in 1775.
Boston Police Commissioner Edward Davis asked people to stay indoors or go back to their hotel rooms and avoid crowds as bomb squads methodically checked parcels and bags left along the race route. He said investigators didn't know whether the bombs were hidden in mailboxes or trash cans.
He said authorities had received "no specific intelligence that anything was going to happen" at the race.
The Federal Aviation Administration barred low-flying aircraft within 3.5 miles of the site.
"We still don't know who did this or why," Obama said at the White House, adding, "Make no mistake: We will get to the bottom of this."
With scant official information to guide them, members of Congress said there was little or no doubt it was an act of terrorism.
"We just don't know whether it's foreign or domestic," said Rep. Michael McCaul, R-Texas, chairman of the House Committee on Homeland Security.
A few miles away from the finish line and around the same time, a fire broke out at the John F. Kennedy Library. The police commissioner said that it may have been caused by an incendiary device but that it was not clear whether it was related to the bombings.
The first explosion occurred on the north side of Boylston Street, just before the finish line, and some people initially thought it was a celebratory cannon blast.
When the second bomb went off, spectators' cheers turned to screams. As sirens blared, emergency workers and National Guardsmen who had been assigned to the race for crowd control began climbing over and tearing down temporary fences to get to the blast site.
The bombings occurred about four hours into the race and two hours after the men's winner crossed the finish line. By that point, more than 17,000 of the athletes had finished the marathon, but thousands more were still running.
The attack may have been timed for maximum carnage: The four-hour mark is typically a crowded time near the finish line because of the slow-but-steady recreational runners completing the race and because of all the friends and relatives clustered around to cheer them on.
Runners in the medical tent for treatment of dehydration or other race-related ills were pushed out to make room for victims of the bombing.
A woman who was a few feet from the second bomb, Brighid Wall, 35, of Duxbury, said that when it exploded, runners and spectators froze, unsure of what to do. Her husband threw their children to the ground, lay on top of them and another man lay on top of them and said, "Don't get up, don't get up."
After a minute or so without another explosion, Wall said, she and her family headed to a Starbucks and out the back door through an alley. Around them, the windows of the bars and restaurants were blown out.
She said she saw six to eight people bleeding profusely, including one man who was kneeling, dazed, with blood trickling down his head. Another person was on the ground covered in blood and not moving.
"My ears are zinging. Their ears are zinging," Wall said. "It was so forceful. It knocked us to the ground."
Competitors and race volunteers were crying as they fled the chaos. Authorities went onto the course to carry away the injured, while race stragglers were rerouted away from the smoking site.
Roupen Bastajian, a state trooper from Smithfield, R.I., had just finished the race when he heard the blasts.
"I started running toward the blast. And there were people all over the floor," he said. "We started grabbing tourniquets and started tying legs. A lot of people amputated. ... At least 25 to 30 people have at least one leg missing, or an ankle missing, or two legs missing."
The race honored the victims of the Newtown, Conn., shooting with a special mile marker in Monday's race.
Boston Athletic Association president Joanne Flaminio previously said there was "special significance" to the fact that the race is 26.2 miles long and 26 people died at Sandy Hook Elementary School.
Associated Press writers Jay Lindsay, Steve LeBlanc, Bridget Murphy and Meghan Barr in Boston; Julie Pace, Lara Jakes and Eileen Sullivan in Washington; and Marilynn Marchione in Milwaukee contributed to this report.
History of U.S. bombings, failed attempts
Here is a list of some of the worst bombings in the U.S. dating to the 1800s, including some famous attempts that failed:
- April 15, 2013: Two bombs explode in the packed streets near the finish line of the Boston Marathon, killing two people and injuring at least 120.
- Jan. 17, 2011: A backpack bomb is placed along a Martin Luther King Day parade route in Spokane, Wash., meant to kill and injure participants in a civil rights march, but is found and disabled before it can explode. White supremacist Kevin Harpham is convicted and sentenced to 32 years in federal prison.
- May 1, 2010: Pakistani immigrant Faisal Shahzad leaves an explosives-laden SUV in New York's Times Square, hoping to detonate it on a busy night. Street vendors spot smoke coming from the vehicle and the bomb is disabled. Shahzad is arrested as he tries to leave the country and is sentenced to life in prison.
- Dec. 25, 2009: The so-called "underwear bomber," Nigerian Umar Farouk Abdulmutallab, is subdued by passengers and crew after trying to blow up an airliner heading from Paris to Detroit using explosives hidden in his undergarments. He's sentenced to life in prison.
- Sept. 11, 2001: Four commercial jets are hijacked by 19 al-Qaida militants and used as suicide bombs, bringing down the two towers of New York City's World Trade Center and crashing into the Pentagon. Nearly 3,000 people are killed in New York, Washington and Pennsylvania.
- Jan 22, 1998: Theodore Kaczynski pleads guilty in Sacramento, Calif., to being the Unabomber in return for a sentence of life in prison without parole. He's locked up in the federal Supermax prison in Colorado for killing three people and injuring 23 during a nationwide bombing spree between 1978 and 1995.
- Jan. 20, 1998: A bombing at an abortion clinic in Birmingham, Ala., kills one guard and injures a nurse. Eric Robert Rudolph is suspected in the case.
- July 27, 1996: A bomb explodes at Centennial Olympic Park in Atlanta during the Summer Games, killing two people and injuring more than 100. Eric Robert Rudolph is arrested in 2003. He pleads guilty and is sentenced to life in prison.
- April 19, 1995: A car bomb parked outside the Murrah Federal Building in Oklahoma City kills 168 people and injures more than 500. It is the deadliest U.S. bombing in 75 years. Timothy McVeigh and Terry Nichols are convicted. McVeigh is executed in 2001 and Nichols is sentenced to life in prison.
- Feb. 26, 1993: A bomb in a van explodes in the underground World Trade Center garage in New York City, killing six people and injuring more than 1,000. Five extremists are eventually convicted.
- Nov. 7, 1983: A bomb blows a hole in a wall outside the Senate chamber at the Capitol in Washington. No one is hurt. Two leftist radicals plead guilty.
- May 16, 1981: A bomb explodes in a men's bathroom at the Pan Am terminal at New York's Kennedy Airport, killing a man. A group calling itself the Puerto Rican Armed Resistance claims responsibility. No arrests are made.
- Dec. 29, 1975: A bomb hidden in a locker explodes at the TWA terminal at New York's LaGuardia Airport, killing 11 people and injuring 75. Palestinian, Puerto Rican and Croatian groups are suspected, but no arrests are made.
- Jan. 29, 1975: The U.S. State Department building in Washington, D.C., is bombed by the radical left group Weather Underground. No one is killed.
- Jan. 24, 1975: A bomb goes off at historic Fraunces Tavern in New York City, killing four people. It was one of 49 bombings attributed to the Puerto Rican nationalist group FALN between 1974 and 1977 in New York.
- Jan. 27, 1972: A bomb wrecks the New York City office of impresario Sol Hurok, who had been booking Soviet artists. One person is killed and nine are injured, Hurok among them. A caller claiming to represent Soviet Jews claims responsibility, but no arrests are made.
- March 1, 1971: The Senate wing of the U.S. Capitol Building in Washington, D.C., is bombed by the radical left group Weather Underground. No one is killed.
- March 6, 1970: Three members of the Weather Underground accidentally blow themselves up in their townhouse in New York City's Greenwich Village while making bombs.
- Sept. 16, 1963: Four black girls are killed in a bombing at Birmingham, Ala.'s Sixteenth Street Baptist Church. Years later, juries convicted three Ku Klux Klansmen and one suspected accomplice died without ever having been charged. One of the four is still in prison and the others are dead.
- 1951-56: George Metesky, a former Consolidated Edison employee with a grudge against the company, sets off a series of blasts at New York landmarks, including Grand Central station and Radio City Music Hall. No one is killed. Known as The Mad Bomber, Metesky spends 16 years in a mental hospital.
- May 18, 1927: 45 people - 38 of them children - are killed when a school district treasurer, Andrew Kehoe, lines the Bath Consolidated School near Lansing, Mich., with hundreds of pounds of dynamite, and blows it up. Investigators say Kehoe, who also died in the blast, thought he would lose his farm because he couldn't pay property taxes used to build the school.
- Sept. 16, 1920: A bomb explodes in New York City's Wall Street area, killing 40 and injuring hundreds. Authorities conclude it was the work of "anarchists" and come up with a list of suspects, but all flee to Russia.
- Oct. 1, 1910: The Los Angeles Times building is dynamited during a labor dispute, killing 20 people. Two leaders of the ironworkers union plead guilty.
- May 4, 1886: A bomb blast during a labor rally at Chicago's Haymarket Square kills 11 people, including seven police officers, and injures more than 100. Eight "anarchists" are tried for inciting riot. Four are hanged, one commits suicide and three win pardons after seven years in prison.
History compiled by AP News Researchers Jennifer Farrar and Susan James.
Mass sporting events and teams hit by attacks
By The Associated Press
A glance at some sporting events and teams that have been affected by attacks and threats:
Sept. 5-6, 1972 - Palestinians going by the name of "Black September" kill 11 Israeli athletes at the 1972 Munich Olympics.
April 21, 1987 - A car bomb kills more than 100 people at a bus station in Colombo, Sri Lanka. The blast came during a tour of the country by the New Zealand cricket team. The three-Test tour was cut to one.
Feb. 11, 1996 - Cricket teams from Australia and the West Indies refuse to play preliminary World Cup matches in Sri Lanka a week after a huge bomb blast in Colombo killed 80 people and injures 1,200.
July 27, 1996 - Centennial Park bombing at Atlanta Olympics. The attack took place during a nighttime music concert at the Centennial Olympic Park. The explosion killed one person and injured over 100 others.
April 5, 1997 - The Grand National, the most famous horse race in England, was abandoned after two coded bomb threats were reportedly received from the IRA. Sixty-thousand spectators (including Princess Anne), jockeys, race personnel and local residents were evacuated, and the course was secured by police. The race was run two days later.
May 1, 2002 - Hours before the Champions League semifinal between Real Madrid and Barcelona, a car bomb was detonated near Bernabeu Stadium in Madrid. Seventeen people were injured. UEFA made security checks before going ahead with the match.
May 8, 2002 - A suicide bomber killed 14 people outside the hotel where the New Zealand cricket team was staying in Karachi, Pakistan. Fourteen people died in the attack and the New Zealand team returned home.
2006 - Iraqi sportsmen and women were targeted three times. On May 17, 15 athletes and officials of the Iraqi taekwondo team were kidnapped as they headed to Jordan for a training camp. None of the athletes were seen alive again. On May 26, gunmen shot and killed the Iraqi tennis coach and two of his players. The final attack on July 16 involved 50 gunmen who attacked a sports conference in Baghdad. They kidnapped 30 athletes and officials, including the head of Iraq's Olympic Committee, Ahmed al-Hadjiya.
April 9, 2008 - A suspected Tamil Tiger suicide bomber detonated a device at the start of a marathon celebrating the start of Sri Lanka's new year. Highways minister Jeyaraj Fernandopulle, former Olympic marathon runner KA Karunaratne and the national athletics coach, Lakshman de Alwis, were among the dozen people killed.
Jan. 4, 2008 - The Dakar Rally was canceled for the first time in its 30-year history. The threat of an attack from al Qaeda made the race too risky for the organizers.
March 3, 2009 - The Sri Lankan cricket team bus was attacked by masked gunmen as they traveled in their team bus outside a stadium in Lahore, Pakistan. Seven people were killed in the attack and six of the Sri Lankan cricket players were wounded.
Jan. 8, 2010 - Assistant coach Abalo Amelete and communications director Stanislas Ocloo of the Togo soccer team were killed when gunmen fired on the team's bus in Angola, site of the African Cup of Nations soccer tournament. The Angolan driver was also killed and nine members of Togo's party were wounded including Togo's reserve goalkeeper.
April 15, 2013 - Two bombs exploded in the crowded street near the finish line of the Boston Marathon, killing two people and injuring more than 130 others. The explosions occurred about four hours into the race and about three hours after the men's winner crossed the line. By that point, more than 17,000 of the runners had finished the race, but thousands of others were farther back along the course.