SAN FRANCISCO, Aug 10 (Reuters) - A young Marine involved in the April 2006 killing of a 52-year-old Iraqi man was released following a clemency decision, the Marines said on Friday. Robert Pennington was one of seven Marines and a Navy medic who set out to kidnap and kill a suspected insurgent but instead seized Hashim Ibrahim Awad, a disabled police officer known to support the American occupation, according to defendants' testimony. The death near Hamdania, a rural town in the vast western Iraqi province of Al Anbar, was one of a series in which U.S. forces abused or killed Iraqi civilians under questionable circumstances, damaging the image of U.S. troops abroad. Pennington, 21 at the time of Awad's death, received an eight-year prison sentence in February after pleading guilty to conspiracy and kidnapping. In exchange, prosecutors dropped murder, larceny and housebreaking charges. In making the clemency decision, Lt. Gen. James Mattis balanced a number of factors including the ages of those involved, their military experience and rank, and their level of involvement, the Marines said in a statement.