OAK CREEK, USA (AP) — The gunman who killed six people at a Sikh temple in Wisconsin before being shot to death by police was identified Monday as a 40-year-old Army veteran and former leader of a white supremacist heavy metal band.

Wade Michael Page strode into the temple carrying a 9mm handgun and multiple magazines of ammunition and opened fire without saying a word, authorities said.

Page joined the Army in 1992 and was discharged in 1998, according to a defense official who spoke to The Associated Press on condition of anonymity because he was not yet authorised to release the information.

When the shooting at the Sikh Temple of Wisconsin in suburban Milwaukee ended, six victims ranging in age from 39 to 84 years old lay dead. Three others were critically wounded.

Page was a "frustrated neo-Nazi" who led a racist white supremacist band, according to the Southern Poverty Law Center.

Mark Potok, a senior fellow at the non-profit civil rights organization in Montgomery, Alabama said Page had been on the white-power music scene for more than a decade, playing in bands known as Definite Hate and End Apathy.

"The name of the band seems to reflect what he went out and actually did," Potok said.

"There is a whole underworld of white supremacists music that is rarely seen or heard by the public," Potok said, describing lyrics that talk about carrying out genocide against Jews and other minorities, he said.

Potok said there's no research showing white supremacists hating Sikhs, suggesting Sunday's attack could have been an example of someone mistaking Sikhs for another group, such as Muslims.

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.

He told the website his "inspiration was based on frustration that we have the potential to accomplish so much more as individuals and a society in whole," according to the law center. He did not mention violence.

End Apathy's biography on the band's MySpace page said it was based in Nashville, North Carolina