A picture is emerging of the man suspected of killing six worshippers at a Sikh temple near Milwaukee Sunday that suggests he was a disgruntled white supremacist with a failed military career, a drinking problem and heavy financial debt.

Police in Oak Creek, Wisc. where the massacre occurred, have identified the gunman as 40-year-old Wade Michael Page. He was shot dead by police during Sunday’s rampage.

Page was a member of the U.S. Army from 1992 to 1998 who was discharged after a number of incidents, including being intoxicated while on duty “and going AWOL,” the Associated Press reports.

After leaving the army, it appears Page did little beyond joining hate groups and playing in white supremacist rock bands with names such as “Definite Hate” and “End Apathy.”

At one point, he bought a brick house outside Fayetteville, N.C. The home is now boarded up and a notice taped to the door says the home is in foreclosure and had been sold to a bank in January, AP reports.

Former FBI agent and criminal profiler Brad Garrett says there is often a typical progression of anger among mass shooters. Agitation in a gunman like Page often builds as he experiences life event crises such as like losing a job, or running into financial issues.

“That coupled with his hatred and his inability -- in his mind -- to do anything about it, he apparently reaches a breaking point where he decided he would empower himself and kill what he would define as non-white Americans,” Garrett told CTV’s Canada AM from Washington.

“If he got killed, so be it, but he’d at least become in charge over what he believes. I think some version of that would probably fit Mr. Page,” Garrett said.

The bald, heavily-tattooed Page described himself as a member of the "Hammerskins Nation," a skinhead group rooted in Texas that also has branches in Canada. He posted frequently on Internet forums for skinheads, repeatedly urging members to act more decisively in their cause.

"If you are wanting to meet people, get involved and become active," Page wrote last year. "Stop hiding behind the computer or making excuses."

He told a white supremacist website in a 2010 interview that his inspiration for his music “was based on frustration that we have the potential to accomplish so much more as individuals and a society in whole.”

His activity on hate sites appears to have increased during the last two years, posting more than 250 messages on one skinhead site between March 2010 and the middle of this year.

In an April message, Page said: "Passive submission is indirect support to the oppressors. Stand up for yourself and live the 14 words," a reference to a common white supremacists mantra.

It appears Page didn’t leave behind a manifesto or an angry blog, and Oak Creek Police Chief John Edwards cautioned Monday that investigators might never know what compelled Page to walk into a temple full of strangers and begin shooting.

"We have a lot of information to decipher, to put it all together before we can positively tell you what that motive is -- if we can determine that," Edwards said.

Suburban Milwaukee police had no contact with Page before Sunday, though he did have a brief criminal history in other states, including a misdemeanour criminal mischief conviction in 1994 from an arrest in El Paso, Texas, for getting drunk and kicking holes in the wall of a bar.

He also pleaded guilty to driving under the influence in Colorado in 1999 but never completed a sentence, which included alcohol treatment.

He was arrested on suspicion of drunken driving again in 2010 in North Carolina after running his car off the side of a highway. The case was dropped a year later for lack of evidence.

SITE Monitoring Service, a Maryland-based private intelligence firm that searches the Internet for extremist activity, says they were aware of Page’s online activity on supremacist websites.

Garrett says it’s likely Page was also known to federal intelligence officials.

“Was he part of an intelligence file or database where they keep track of people who talk in extremist ways? The answer is probably yes. But these databases contain the names of hundreds of thousands of people. There isn’t one agent watching each of these people,” he noted.

The FBI is leading the rest of the investigation because the shootings are being treated as “domestic terrorism.”