Former US army soldier Wade Michael Page was on Monday identified as the gunman who killed six people in a shooting rampage at a Wisconsin gurdwara before being shot dead by a police officer on Sunday.
Page was a "psychological operations specialist" in the US army before being dismissed in 1998 after six years of service.
Page, 40, is reported to have been discharged for "patterns of misconduct," officials said. The police are still trying to determine the motive of his killing, but according to the Southern Poverty Law Centre, he led neo-Nazi music group 'End Apathy'.
The police continued to search his apartment. The authorities said they were treating the attack as an "act of terrorism".
An agent from the Bureau of Alcohol, Tobacco and Firearms told ABC News that the shooter had a 9/11 tattoo on his arm.
The news channel also cited unnamed sources who alleged that the shooter was possibly a "skin head" or "white supremacist".
According to officials, Page received his basic training at Fort Sill, Oklahoma, before being moved to Fort Bliss in Texas.
Page was a qualified parachutist who received a commendation medal, five achievement medals, two good conduct medals, the National Defence Service Medal and a Humanitarian Service Medal, officials said.
"The temple shooting was not simply assault on congregation of Sikhs. It was an offence against peaceful, innocent people," top Democratic leader Nancy Pelosi tweeted.
In a blog posting, the Southern Poverty Law Centre said that in 2010, Page gave an interview to white supremacist website Label 56. He had said that when he started the band in 2005, its name reflected his wish to "figure out how to end people's apathetic ways" and start "moving forward".
"I was willing to point out some of my faults on how I was holding myself back," Page had said.
:The victims were five men and one woman aged between 39 and 84. Members of the Sikh community said the president of the congregation and a priest were among the victims.