Thursday, a grieving city is trying to heal.
President Obama and the First Lady joined Boston residents at an interfaith service dedicated to the victims of the Boston marathon bombing.
The President offered support and encouragement.
“You will run again…”, says the President
The 2000 seat cathedral was packed with victims, first responders, government officials and members of the community.
There were prayers for those recovering from injury and tears for the three people who died, 29-year-old Krystle Campbell, Lingzi Lu, a native of China, and 8-year-old Martin Richard.
Runner, Tracey Monroe saw Martin's body, and helped his younger sister who had lost a leg.
Tracy says “I just imagined if my daughter were injured liked that…she was so badly injured.. and so scared and she was so incredibly brave.”
As for the investigation, The FBI has images of two men, both possible suspect and the other a person of interest.
Sources tell ABC News the best view of the person comes from cameras at the Lord and Taylor store.
Janet Napolitano, Secretary of Homeland Security, is asking the public for help in identifying individuals in the video.
FBI agents are also processing hundreds of pieces of evidence recovered from the crime scene, including tiny circuit boards, small nails and the remains of a pressure cooker bomb.
“It's extremely important to match the bomb to the bad guy.” says Brad Garrett, an ABC news Consultant.