Before he strode into a Sikh temple near Milwaukee and killed six people, Wade Michael Page played in white supremacist heavy metal bands with names such as Definite Hate and End Apathy.

A day after the massacre, during which Page was fatally shot by police, the gunman's life emerged in public records and interviews. The bald, heavily tattooed bassist was a 40-year-old army veteran who trained in psychological warfare. He was demoted and discharged more than a decade ago.

On Sunday, Page opened fire on worshippers at a Sikh temple, carrying a 9-mm handgun and multiple magazines of ammunition. His motive was still largely a mystery. So far, no hate-filled manifesto has emerged, nor any angry blog or ranting Facebook entries to explain the attack.

Wade Michael Page, in an undated photo provided by the FBI on Monday, was reportedly the man who shot and killed six people at a Sikh temple in the Milwaukee area. Page was shot by police and died. (M. Spencer Green/Associated Press)

Oak Creek police Chief John Edwards suggested Monday that investigators might never know for certain why the lone attacker targeted a temple full of strangers.

"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.

Page joined the army in 1992 and was discharged in 1998. He was described Monday by the Southern Poverty Law Center as a "frustrated neo-Nazi" who had long been active in the obscure underworld of white supremacist music.

Page wrote frequently on white supremacist websites, describing himself as a member of the "Hammerskins Nation," a skinhead group rooted in Texas that has offshoots in Australia and Canada, according to the SITE Monitoring Service, a Maryland-based private intelligence firm that searches the internet for terrorist and other extremist activity.

In online forums, Page promoted his music while interacting with other skinheads. He posted 250 messages on one site between March 2010 and the middle of this year, and appeared eager to recruit others. In March 2011, he advertised for a "family friendly" barbeque in North Carolina, extolling those online to attend.

"If you are wanting to meet people, get involved and become active, then you really need to attend," he wrote, according to SITE. "Stop hiding behind the computer or making excuses."

In November, Page challenged a poster who indicated he would leave the U.S. if Herman Cain were elected president, writing in reply, "Stand and fight, don't run."

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.

Mark Potok, a senior fellow at the law centre, a nonprofit civil rights organization in Montgomery, Ala., said Page played in groups whose often sinister-sounding names seemed to "reflect what he went out and actually did." The music talked about genocide against Jews and other minorities.

In a 2010 interview, Page told a white supremacist website that he became active in white-power music in 2000, when he left his native Colorado and started the band End Apathy in 2005. The band's MySpace page listed the group as based in Nashville, N.C.

Page joined the military in Milwaukee in 1992 and was a repairman for the Hawk missile system before switching jobs to become one of the army's psychological operations specialists assigned to a battalion at Fort Bragg, N.C.

As a "psy-ops" specialist, Page would have trained to host public meetings between locals and American forces, use leaflet campaigns in a conflict zone or use loudspeakers to communicate with enemy soldiers.

He never deployed overseas in that role, army spokesman George Wright said.

Page was demoted in June 1998 for getting drunk while on duty and going AWOL, two defence officials said, speaking on condition of anonymity because they were not authorized to release information about the gunman.

Page also received extra duty and was fined. The defence officials said they had no other details about the incident, such as how long Page was gone or whether he turned himself in.

CBC's Lyndsay Duncombe, reporting from Oak Creek, Wis., said the FBI made an appeal Monday for tips that could help identify another white male at the scene investigators would like to speak with.

An FBI special agent holds a photograph of a subject that the FBI wants to interview in connection with the weekend deadly shooting at a Sikh temple in Wisconsin. (Darren Hauck/Getty Images)

"This person is not identified as of yet, and we would like to identify this person and talk to him," said FBI special agent Teresa Carlson, holding up a photo of the man. "He is just a person of interest at this time."

Police reiterated their belief that there was only one gunman, Duncombe said, adding that the weapon was purchased legally.

The six people killed in the shootings have been identified as Satwant Singh Kaleka, 65, the temple president; Paramjit Kaur, 41, a mother of two; Suveg Singh Khattra, 84, a former farmer who moved from India in 1994 to join his son; Prakash Singh, 39, a Sikh priest and father of two; and Ranjit Singh, 49, and Sita Singh, 41, brothers and Sikh priests.

Gunman's stepmother recalls 'precious' boy

Outside Fayetteville, N.C., a brick ranch house Page bought in 2007 with help from a Veterans Administration mortgage stood boarded up Monday with knee-high weeds in the yard. A notice taped to the front indicated the home was in foreclosure and had been sold to a bank in January.

'Every Sikh American today is hurting, grieving and afraid.'—Valarie Kaur, who chronicled violence against Sikh Americans in documentary

Before buying the home, Page lived with army soldier Darren Shearlock, his wife and young children in a doublewide trailer in a rural community near Fort Bragg, records show.

Shearlock, dressed in his military fatigues, declined to comment about Page or the shooting when approached Monday by The Associated Press.

Page's former stepmother said she was devastated to learn of the bloodshed.

"He was a precious little boy, and that's what my mind keeps going back to," said Laura Page of Denver, who was divorced from Page's father around 2001.

'Pretty calm' roommate

In Wisconsin, Page responded to a recent online ad seeking a roommate in Cudahy, a small city outside Milwaukee.

He rented a room in Kurt Weins's house in June, telling Wein he had recently broken up with his girlfriend and needed a place to stay.

Weins said Page stayed in that room all the time, declining invitations to watch TV with him. Several weeks later, Page rented an apartment in a duplex owned by Weins across the street. Page explained that he wanted to bring some belongings out of storage.

"We talked, but it was really about nothing," Weins said. "He seemed pretty calm. He didn't seem like the type to raise his voice."

Indian Sikhs in New Delhi sit and pray on Monday to protest Sunday's killing of several people at a Milwaukee-area Sikh temple in the United States. (Manish Swarup/Associated Press)

After the FBI searched the apartment in the duplex, Weins returned and found only a computer desk, chair and an inflatable mattress.

Suburban Milwaukee police had no contact with Page before Sunday, and his record gave no indication he was capable of such intense violence.

The FBI was leading the investigation because the shooting was considered domestic terrorism. The agency said it had no reason to believe anyone other than Page was involved.

Page entered the temple as several dozen people prepared for Sunday services. He opened fire without saying a word.

The president of the temple died defending the house of worship he founded.

Victim tried to stop gunman with butter knife

Satwant Singh Kaleka, 65, managed to find a simple butter knife in the temple and attempted to stab the gunman before being shot twice, his son said Monday.

Amardeep Singh Kaleka said FBI agents hugged him, shook his hand and told him his father was a hero.

"Whatever time he spent in that struggle gave the women time to get cover" in the kitchen, Kaleka said.

Federal officials said the gun used in the attack had been legally purchased. Page was issued five pistol-purchase permits in 2008 in North Carolina, paying a $5 fee for each.

U.S. President Barack Obama said Monday that Americans are "heartbroken" by the tragedy and would "recoil" if the victims' ethnicity turns out to be have been a factor in the shootings.

"It is important to reaffirm that regardless of what we look like or where we come from or where we worship, we are all one people and we look after one another in this country," Obama told reporters in the Oval Office.

The president pledged to "examine additional ways to reduce violence" but stopped short of calling for new gun-control laws.

On Sunday, the first officer to respond was shot eight to nine times as he tended to a victim outside the temple. A second officer then exchanged gunfire with the suspect, who was fatally shot.

The six dead ranged in age from 39 to 84 years old. Three people were critically wounded, including the police officer.

Online records show Page had a brief criminal history in other states, including pleading guilty to misdemeanour criminal mischief after a 1994 arrest in El Paso for getting drunk and kicking holes in the wall of a bar. He received six months probation.

Page also pleaded guilty to driving under the influence in Colorado in 1999 but never completed a sentence that included alcohol treatment, records show.

Page was arrested on suspicion of drunk 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, according to court records.

With files from CBC News