GUNMAN Gavin Long, who killed three police officers in Baton Rouge, Louisiana, on Sunday before being shot dead, was revealed yesterday to have served in the US Marine Corps from 2005 to 2010.

Military records show the African-American former sergeant was posted to Iraq from June 2008 to January 2009.

While in the military, he was awarded several medals, including one for good conduct, and received an honourable discharge. His occupational expertise was listed as “data network specialist.”

Louisiana state police spokesman Colonel Mike Edmonson said that Mr Long had definitely been “seeking out” police to shoot.

“His movements, his direction, his attention was on police officers,” he added.

The gunman had travelled from Kansas City, Missouri, to Baton Rouge to carry out the attack.

Examination of online posts made by someone using Mr Long’s alias Cosmo Setepenra revealed comments that protests alone do not work and that people must fight back in response to the deaths of black men at the hands of police.

Mr Long sought to change his name to Cosmo Setepenra last year and a website bearing that name links to online books about nutrition, self-awareness and empowerment.

The man describes himself as a “freedom strategist, mental game coach, nutritionist, author and spiritual adviser.”

He says: “You’ve got to fight back. That’s the only way a bully knows to quit.”

In an earlier video, the man says that, if anything happens to him, he doesn’t want to be linked to any groups, though he mentions once belonging to Nation of Islam.