BOSTON - An army of federal agents raced to find out who attacked the city's historic marathon, leaving three dead and more than 100 injured amid a war zone of shattered glass and bomb debris on Patriots Day.
Hundreds of photos and videos have documented the events of Monday afternoon at the Boston Marathon, but there is total mystery over who did it and why. (AP Photo)
Police issued an alert for a rental van that may have tried to gain access to the finish line area and for a man in dark clothing and a hood seen leaving the scene shortly before the blast, reported the NBC TV network.
Surveillance video showed a hooded figure carrying two backpacks at about that time.
The deadly explosions reverberated on both sides of the Atlantic as cities from Los Angeles to London to Bangkok saw a surge in security.
- Bangkok responds: Security checks increased
As of Tuesday morning, no persons or group had claimed credit for twin explosions at the finish line near Boston's Copley Square. The Pakistani Taliban, a group that has threatened the United States in the past, denied participation, according to the Associated Press.
Law enforcement officials questioned an injured Saudi national at a local hospital, but news stories indicated that the individual appears to have no connection to the case. The Boston Globe reported that he was simply a frightened spectator who had tried to flee but was tackled and restrained by bystanders.
On Monday night agents from the FBI, the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), and other law enforcement agencies raided a unit in a high-rise apartment on Ocean Drive in the seaside Boston suburb of Revere. They removed several bags, including what appeared to be a large duffel bag, but would not discuss any details with the media.
US Congressman William Keating of Massachusetts, a member of the House Homeland Security Committee, told a local TV reporter that the two bombs at the finish line, which exploded seconds apart, had been stashed in trash receptacles and were clearly a "coordinated attack."
Authorities discovered two other unexploded devices, the Democratic Party congressman told Boston's WBZ News. But other reports said no unexploded devices had been found.
Among the dead is 8-year-old Martin Richard, whose father was running in the race. The boy's mother and sister were also gravely injured, according to a Boston Globe report. The family had gathered at the finish line for cheers and celebrations.
Although President Obama did not use the word "terrorism" in remarks to the nation Monday evening, other US officials made it clear that the bombing is being treated as a terrorist attack. That would make it the first such strike on US soil since Sept. 11, 2001, and a deadly reminder that it is impossible to armor all national activities against a terrorist threat.
One thing is clear: The bomber or bombers were not highly skilled. The explosive devices were relatively crude compared with those produced overseas by Al-Qaeda or other radical Islamist terrorist groups, RAND Corp terror expert Brian Jenkins told Los Angeles television. They were much smaller than the powerful truck bomb that Timothy McVeigh used to devastate the federal building in Oklahoma City in April 1995.
In that sense they were analogous to the pipe bombs that killed two and injured 100 in 1996 at Atlanta's Centennial Park during the Olympics.
But the reaction was different, and this time was worldwide.
The White House, New York's Times Square, and the preparations for former Prime Minister Margaret Thatcher's funeral in London all had enhanced and intensified law enforcement presence after Monday's two blasts in Boston.
Police in Los Angeles, Washington, DC, Detroit, San Diego and Las Vegas monitored landmarks, government buildings, transit hubs and sporting events. Law enforcement agencies also urged the public via Twitter and Facebook to report suspicious activity to the police.
British police were also reviewing security plans for Sunday's London Marathon - the next major international race - because of the bombs that killed three people and injured more than 140 in Boston.In Washington, Secretary of Homeland Security Janet Napolitano urged the American public "to be vigilant and to listen to directions from state and local officials."
At the White House, the Secret Service expanded its security perimeter after the attacks, shutting down Pennsylvania Avenue and cordoning off the area with yellow police tape. Several Secret Service patrol cars blocked off entry points, although the White House was not on lockdown and tourists and other onlookers were still allowed in the park across the street.