One Boston marathon bombing suspect has been shot dead and another is on the loose, police have said.
It follows a shootout in Watertown between the two suspects and dozens of armed officers after a policeman was shot dead at Massachusetts Institute Of Technology, nine miles from Boston city centre.
Boston Police commissioner Ed Davis said: "What we are looking for right now is a suspect consistent with the description of suspect number two - the white-capped individual who was involved in Monday's bombing of the Boston Marathon.
He is described as light-skinned with brown wavy hair and dressed in a grey hooded top.
"You have seen the picture, You all have it. That's the individual we are looking for at this moment."