Photos of suspects in the Boston Marathon bombings are seen during a news conference in Boston, Massachusetts April 18, 2013.
BOSTON — Investigators released pictures of two suspects in the Boston bombing on Thursday, seeking the public's help in finding two men photographed on the crowded sidewalk before Monday's bombs exploded near the finish line.
"Today we are enlisting the public's help to identify the two suspects," Richard DesLauriers, the U.S. Federal Bureau of Investigation's special agent in charge in Boston, told a news conference.
Both men carried backpacks that were believed to contain the bombs. The man identified as suspect No. 1 wore a dark baseball cap. Suspect No. 2 wore a white cap backwards and was seen setting down his backpack on the ground, DesLauriers said.
"Somebody out there knows these individuals as friends, neighbors, co-workers or family members of the suspects. Though it may be difficult, the nation is counting on those with information to come forward and provide it to us," he said.
The bombings began a week of security scares that rattled the United States and evoked memories of the September 11, 2001 hijacked plane attacks. Three people were killed and 176 injured in the Boston bombings.
President Barack Obama sought to bring solace to Boston and the nation in an interfaith service at a cathedral about a mile from the bomb site, declaring "You will run again" and vowing to catch whoever was responsible.
He promised resilience in a message directed toward Boston but also to a country that was on edge.
A man was arrested on Wednesday on suspicion of mailing the deadly poison ricin to Obama and a massive explosion at a fertilizer factory devastated a small Texas community, sending shockwaves at least 50 miles away.
Some of the victims of the Boston attack suffered gruesome injuries, and at least 10 lost limbs as a result of the blasts. Investigators believe the bombs were made of pressure cookers packed with shrapnel.
"As you begin this long journey of recovery, your city is with you, your commonwealth is with you, your country is with you," Obama said. "We will all be with you as you learn to stand and walk and, yes, run again. Of that, I have no doubt. You will run again."
After his speech, Obama met with volunteers and Boston Marathon organizers, many of whom cared for the injured, and with victims at Massachusetts General Hospital.
MOBILE USERS: Click here to view the photos.
MOBILE USERS: Click here to view the surveillance video.