Baton Rouge - Gavin Long considered himself a spiritual leader and revolutionary, a man willing to take action while others focused on protests.Long, who killed two police officers and a sheriff's deputy in Baton Rouge on Sunday, was a college-educated former Marine sergeant who served in Iraq, receiving a medal for good conduct. But he also created an erratic online persona known as Cosmo Setepenra, ranting about what he considered oppression and advocating for violence."You've got to fight back. That's the only way a bully knows to quit. He doesn't know words ... The serious ones, the real ones, the alpha ones, we know what it's going to take. It's only fighting back, or money. That's all they care about, revenue and blood," he said in one recent video.The black man whose last known address was in Kansas City, Missouri, carried out the attack on his 29th birthday. Police say he was seeking out law enforcement officers and ambushed them, wounding three other officers before he was killed in the latest in a string of violent encounters involving police.Long expressed his intention to legally change his name to Cosmo Setepenra in a non-binding document filed in May 2015 with the Jackson County Recorder of Deeds Office. He never made the name-change request in court as is required, Jackson County spokesperson Brenda Hill said.In the document, he also says he belongs to the Washitaw de Dugdahmoundyah, also known as the Washitaw Nation.The Southern Poverty Law Centre said on its blog that the Washitaw Nation is a black anti-government group whose members believe they are indigenous to the United States and beyond the federal government's reach.In the document filed in Jackson County, Long writes: "Under common law, an adult or emancipated person has the right to change his or her name without legal formality or permission of court to any name he or she lawfully chooses."It also says: "I AM restored to my own aboriginal-indigenous appellation ... without colourable law [legal] contract from GAVIN EUGENE LONG to Cosmo Ausar Setepenra in accord with the laws, customs, religious practices, traditions, distinct identities, characteristics and divine principles and language[s] of my Ancestors ..."Motive Asked about Long's ties to the Washitaw Nation, FBI spokesperson Bridget Patton said it's too early to draw conclusions about motive.Posting online as Setepenra, Long called himself a "Freedom Strategist, Mental Game Coach, Nutritionist, Author and Spiritual Advisor" who wrote online books he described as lessons about nutrition, self-awareness and empowerment.And in rambling online videos and written posts, he discussed topics ranging from what he considered the extermination of Native Americans to the United States' fight for independence. He said that it is celebrated when "Europeans" fight oppression, "but when an African fights back, he's wrong".In a video posted July 10, Long said he was speaking from Dallas after another black man killed five police officers there. He said he had already decided to travel to the city before the shooting, and guessed that "the spiritual was just telling me it was the right place to come".Long also discussed protests in Baton Rouge. He urged listeners to question their "mindsets" and fight back, insisting that protests alone don't work."You see, that's what separates me from the 7 billion. And that's why I'm so powerful because I stand on my rights," he said.Honourable dischargeWhile little is known about his early life, military records show that Long was a Marine from 2005 to 2010, attaining the rank of sergeant. He served in Iraq from June 2008 to January 2009, and records show he received several medals during his military career, including one for good conduct. Long, who received an honourable discharge, was listed as a "data network specialist" in the Marines.In San Diego, Long attended a location of Central Texas College at the Marine Corps Air Station Miramar and also took online classes from 2007 to 2011, receiving an associate of arts degree in general studies, according to Bruce Vasbinder, a spokesperson for the school that has locations around the world. Vasbinder said he did not have disciplinary records at hand and wasn't aware of any problems with Long.After the Marines, Long attended the University of Alabama for one semester, in the spring of 2012, according to university spokesperson Chris Bryant. University police had no interaction with Long during that time, Bryant said. He was also briefly enrolled at Clark Atlanta University during the 2012-13 academic year, the school said.Long said in posts attributed to Cosmo Setepenra that he had also spent time in Africa.In the last message sent from his Twitter account on Saturday, Long wrote: "Just bc you wake up every morning doesn't mean that you're living. And just bc you shed your physical body doesn't mean that you're dead."Sunday's attack was the latest in a series of deadly encounters in the United States involving police and black men that have prompted a national debate over race and policing. It also came less than two weeks after 37-year-old Alton Sterling, a black man, was fatally shot by police in Baton Rouge in a confrontation that sparked nightly protests. Police-community relations in Baton Rouge have been especially tense since Sterling's death.In southeastern Kansas City, police converged on a small turquoise frame house listed under Long's name. An Associated Press reporter observed officers with weapons drawn behind trees and others behind marked and unmarked police cars in the residential neighbourhood.Missouri court records show that a Gavin Eugene Long filed a petition for divorce from his wife in February 2011. The records don't say why the couple divorced, but the petition indicates they had no children and that Long had represented himself. Three months after the divorce petition was filed, his ex-wife was granted restoration of her maiden name.Last month, on June 7, a case against Long by the city of Kansas City over unpaid city earnings taxes was dismissed.