A Baton Rouge Police officers patrol pours water on his head on Airline Hwy after 3 police officers were killed early this morning on July 17, 2016 in Baton Rouge, Louisiana. According to reports, one suspect has been killed while others are still being sought by police. [Photo/VCG]

WASHINGTON - A former US Marine sergeant who served in Iraq has been identified as the gunman who killed three police officers and wounded three others in Baton Rouge, Louisiana, on Sunday, according to a government source with knowledge of the investigation.

Another source familiar with the investigation said that the suspect, Gavin Long, 29, was from Kansas City, Missouri. The source said there was reason to believe a 911 call may have been used to lure police to the shooting scene, and that the possibility it had been a conspiracy was being examined by investigators.

Officials speaking publicly have not yet released the name of the suspected killer or any details, beyond saying they believed the single shooter was killed in the shootout.

Long, who was black, was affiliated with the anti-government New Freedom Group, the Wall Street Journal reported, citing a person briefed on the investigation. A spokeswoman for the Southern Poverty Law Center, which tracks extremist groups, said she had no information about that.

Sunday was Long's 29th birthday, according to the Kansas City Star newspaper.

He served in the Marines for five years, from August 2005 to August 2010, and rose to the rank of sergeant, according to Yvonne Carlock, deputy public affairs officer for the U.S. Marines. Long was deployed to Iraq from June 2008 to January 2009.

CBS News reported that Long left the Marines with an honorable discharge. Carlock would not confirm that detail.

Public records show Long had lived in Kansas City and Grandview, Missouri, as well as San Diego and Tuscaloosa, Alabama.