The FBI released photos and video of two suspects in the deadly Boston Marathon bombings and asked for the public's help in identifying the men. The agency's website crashed within moments Thursday.
FBI Agent Richard DesLauriers said the images are from surveillance cameras near the explosion sites shortly before Monday's blasts at the world's most famous marathon. The man in the white cap is seen setting down a backpack at one site near the finish line, DesLauriers said.
"We consider them to be armed and extremely dangerous," DesLauriers said, asking the public not to approach the men. He said there is no additional danger that the FBI knows of at the moment.
Monday's blasts killed three, including a student from China, and injured more than 180.
The images came out hours after President Barack Obama promised a grieving city to hunt down whoever was responsible.
The images show two young-looking men wearing baseball caps, wearing jackets and carrying backpacks along the race route and weaving through the crowd.
"Each piece moves us toward justice," DesLauriers said of the latest information to emerge.
Generally, law enforcement agencies release photos of suspects only as a last resort, when they need the public's help. Releasing photos can tip off a suspect and deny police the element of surprise. It can also trigger an avalanche of tips, forcing police to waste time chasing them down.
At an interfaith service honoring the victims, Obama called the perpetrators of the attack "these small, stunted individuals who would destroy instead of build."
The blasts killed 8-year-old Martin Richard, 29-year-old Krystle Campbell and Lu Lingzi, a graduate student from China. Seven victims remained in critical condition.
The bombs were crudely fashioned from ordinary kitchen pressure cookers packed with explosives, nails and ball bearings, investigators and others close to the case said. Investigators suspect the devices were then hidden in duffel bags and left on the ground.
They exploded within 15 seconds of each other near the finish line at a high-traffic time when thousands of runners were pouring in.
Several media outlets had reported that a suspect had been identified from surveillance video taken at a Lord & Taylor department store between the sites of the bomb blasts.
The investigation will probably collect about a million hours of videotape from fixed security cameras and cellphones and cameras used by spectators, said Gene Grindstaff, a scientist at Intergraph Corp., a company that makes video analysis software used by the FBI and other law enforcement agencies.