Iraqi insurgent group which has claimed responsibility for the downing this week of a US helicopter in central Baghdad that killed five Americans, posted on Thursday a video tape on an Islamic Web site showing footage of the helicopter wreckage and two bodies. The 74 second long video carried the logo of the 1920 Revolution Brigades, a known Sunni militant group. It showed wreckage of a helicopter with bricks scattered around it. The bodies of two men, their torsos naked, one with gray hair and the other dark haired, were seen lying next to one another beside the wreckage. "Our heroes were able to shoot the film of the helicopter wreckage after they downed it over a roof of a house of a citizen," said the insurgent group's statement. Iraqi and US officials said earlier that four of the five Americans who died in the downing of a US security company's helicopter in a dangerous Sunni neighborhood in central Baghdad on Tuesday were shot in the head execution-style - though it was unclear if they were alive when shot.