A former U.S. Marine has been identified as the gunman who killed three police officers Sunday in Baton Rouge, Louisiana. The gunman was killed by police officers during the attack. Three other officers were injured. One remains in critical condition. The suspect, Gavin Long of Kansas City, Missouri, turned 29 on Sunday. He was dressed in black and wearing a mask when he opened fire on officers with an assault rifle. Long served in the U.S. Marines from 2005 to 2010, reaching the rank of sergeant. He was deployed to Iraq from 2008 to 2009. The officers were killed after responding to a report of a man carrying an assault weapon. Colonel Mike Edmonson is head of the Louisiana State Police. He said Monday the gunman ambushed officers and “certainly was seeking out police.” He added: “His movements, his direction, his attention was on police officers.”