Survivors, first-responders and public officials have observed a moment of silence near the Boston Marathon finish line to mark the moment two pressure cooker bombs exploded a year ago.
Three people were killed and 260 others injured in the attacks. MIT police officer Sean Collier was killed several days later, allegedly by the bombing suspects.
This year's running of the Boston Marathon, expected to be the second-largest in history, will take place on Monday.
About 2,500 people attended an invitation-only tribute at the Hynes Convention Center, then walked in the rain to the finish line for the moment of silence. Bells were rung and a flag was raised by Officer Richard Donohue, who was badly injured during a shootout with the bombing suspects.