NEW : Spectator Steve Byrne was standing with a group of friends near a mailbox when the second blast went off . Authorities ask federal and state agents to help identify 3 men seen in photos . NEW : The men are of `` high interest '' in the probe into the Boston Marathon blasts . NEW : two of the men is seen in photos carrying a black backpack , an official says . 2 people were killed and 3 injured when two bombs went off near the finish line .
NEW : Authorities ask federal and state agents to help identify 3 men seen in photos . NEW : The men are of `` high interest '' in the probe into the Boston Marathon blasts . NEW : two of the men is seen in photos carrying a black backpack , an official says . 2 people were killed and 3 injured when two bombs went off near the finish line .