(CBS News) WASHINGTON - After Sunday's shooting at a Sikh temple in Wisconsin that killed six and critically wounded several others, authorities are trying to get a handle on who the gunman was.
Sources say the FBI is looking into the music background of Wade Michael Page to determine if hate was the motive behind the Sikh temple shooting spree.
In a 2010 interview with a white supremacist website, Page said he played with a number "white power" bands, including one called Definite Hate. Page also founded a band named End Apathy.
Mark Potok, who tracks hate groups for the Southern Poverty Law Center, calls Page a frustrated Neo-Nazi who had connections to multiple racist organizations.
"My sense is that we are not talking about someone who was on the fringes of the scene, but really someone who is in the thick of the white supremacist world and especially the music world," Potok said.
Sources say that, several years ago, federal officials came across Page's name as they conducted various investigations, but Page himself was never a target. And no intelligence surfaced suggesting Page posed any threat.
"We had no reason to believe, as far as I know, that any law enforcement agencies had any reason to believe that he was planning or plotting, or capable of such violence," said Special Agent Terese Carlson, who is running the temple shooting investigation for the FBI.
Page did have a minor police record -- convictions for criminal mischief and arrests for "driving under the influence." He was demoted then discharged from the Army in 1998 for being drunk on duty and absent without leave.
But, whatever led up to Sunday's deadly assault apparently happened quickly. Sources say Page bought the 9 mm pistol used in the attack from The Shooters Shop in West Allis, Wisc., on July 28 and picked it up July 30, just a week before the shootings.
Whatever the motive, investigators strongly believe Page acted alone -- yet another case of a lone wolf gunman.