President Barack Obama has told a memorial service for victims of the Boston marathon bombing the attack's perpetrators will be held accountable.
He told an interfaith service that everyone had been touched by the attack on their beloved city.
His visit comes as investigators found clear video images of two potential suspects carrying black bags.
Two bombs were detonated near the finish line on Monday, killing three people and injuring more than 170.
Before the memorial service, host Aaron Schachter talked with people in Boston about the bombing.