FBI releases images of 2 men at Boston Marathon

BOSTON -- The FBI released photos and video Thursday of two suspects in the Boston Marathon bombing and asked for the public's help identifying them, zeroing in on the two men on surveillance-camera footage less than three days after the deadly attack.

FBI agent Richard DesLauriers said the photos of the two men came from surveillance cameras near the explosion sites. One man is seen wearing a dark baseball cap, the other a white cap worn backward.

The man in the white cap is seen setting down a backpack at the site of one of the blasts, DesLauriers said.

Within moments of the announcement, the FBI website crashed, perhaps because of a crush of visitors.

Photos of one of two suspects sought in the Boston Marathon bombing is displayed during a news conference talking about the investigation of the Boston Marathon explosions, Thursday, April 18, 2013, in Boston. The city continues to cope following Monday's explosions near the finish line of the marathon. (AP Photo/Julio Cortez)

The images were released hours after President Barack Obama and first lady Michelle Obama attended an interfaith service at a Roman Catholic cathedral in Boston to remember the three people killed and more than 180 wounded in the twin blasts Monday at the marathon finish line.

Called upon to console a grieving city and reassure a shaken nation, President Barack Obama promised that Boston would "run again" after deadly twin bombings at its famous marathon. More than 2,000 people rose in a standing ovation in the Cathedral of the Holy Cross and sang "America the Beautiful."

Obama's message of resolve in time of tragedy was echoed by Mayor Thomas Menino and Gov. Deval Patrick at a packed interfaith service.

"Nothing will take us down because we take care of one another," Menino said. "Even with the smell of smoke in the air and blood in the streets and tears in our eyes, we triumphed over that hateful act."

In the midst of an emotional and trying stretch for the country and his presidency, Obama vowed to track down those responsible and lauded Boston's "undaunted" spirit.

"Your resolve is the greatest rebuke to whoever committed this heinous act," he told the gathering.

Indeed, Obama's words underscored the stark reality that has left many Americans jittery.

Speaking from the pulpit in the soaring cathedral, the president didn't explicitly declare the deadly marathon explosions an "act of terror" as he did earlier in the week during remarks at the White House. But he showed little restraint in describing those responsible for the attack, calling them "small, stunted individuals."

"Yes, we will find you, and yes, you will face justice," he said, as the crowd applauded.

Also in the crowd was Obama's former presidential rival, Mitt Romney, who served one term as Massachusetts governor.

The break in the investigation came just days after the attack that raised the specter of another terrorist attack on U.S. soil.

The suspects are considered armed and extremely dangerous, DesLauriers said, and people who see them should not approach them.

"Do not take any action on your own," he warned.

Generally, law enforcement agencies release photos of suspects only as a last resort, when they need the public's help in identifying or capturing someone.

Releasing photos can be a mixed bag: It can tip off a suspect and deny police the element of surprise. It also can trigger an avalanche of tips, forcing police to waste valuable time chasing them down.

At the Cathedral of the Holy Cross earlier in the day, Obama declared to the people of Boston: "Your resolve is the greatest rebuke to whoever committed this heinous act." He spoke in almost mocking terms of those who commit such violence.

"We finish the race, and we do that because of who we are," the president said to applause. "And that's what the perpetrators of such senseless violence -- these small, stunted individuals who would destroy instead of build and think somehow that makes them important -- that's what they don't understand.

"We will find you," he warned those behind the attack.

Seven victims remained in critical condition. Killed were 8-year-old Martin Richard of Boston, 29-year-old restaurant manager Krystle Campbell of Medford, Mass., and Lu Lingzi, a 23-year-old Boston University graduate student from China.

The investigation probably will 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 Huntsville, Ala., company that makes video analysis software used by the FBI and other law enforcement agencies.

After years of investigating terrorist incidents and other crimes, the FBI is practiced at cataloging, categorizing and analyzing such evidence and will winnow it dramatically, he said.

"Back in the days of 20 years ago, you were lucky if you had video and it was probably of poor quality and it took a tremendous amount of enhancement. Today you have a completely different issue," Grindstaff said.

Investigators can set the video analysis software so that it automatically searches for certain types of objects or people matching a height and weight description. The software can also spot patterns that analysts might not notice, such as a certain car that turns up in different places, Grindstaff said.

Video and photos recovered in the investigation are being examined and enhanced by an FBI unit called the Operational Technologies Division, said Joe DiZinno, former director of the FBI lab in Quantico, Va.

DiZinno, who ran the FBI lab from 2007 to 2010, said any retrieved bomb components such as the pressure cookers, shrapnel and pieces of timers or wire will be closely examined for fingerprints, DNA, hairs and fibers.

The bomb components would be traced by figuring out the item's maker, where each piece is typically purchased and whether the device resembles any bombs the FBI has seen in past attacks. The FBI lab keeps a detailed file on past bombings, including many overseas attacks.

"Let's say there was a timer," DiZinno said. "Was there a serial number? Who was the manufacturer? That can provide leads for investigators."

One pressure cooker maker, the Fagor Group in Spain, said that it has been contacted by U.S. investigators and that company officials are extending full cooperation. The company sells 250,000 pressure cookers a year in the U.S. and 1 million worldwide.