The gunman who murdered six people inside a US Sikh temple was a neo-Nazi white supremacist extremist.

Former soldier Wade Page walked into the Sikh Temple of Wisconsin and opened fire as several dozen people prepared for Sunday morning services. Six were killed, and three were critically wounded.

Page, 40, was a “frustrated neo-Nazi” who led a racist white supremacist band, the watchdog Southern Poverty Law Centre said.

Page told a white supremacist website in an interview in 2010 that he had been part of the white power music scene since 2000, when he left his native Colorado and started the band, End Apathy, in 2005, the civil rights organisation said.

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 SPLC. He did not mention violence in the interview.

Page joined the military in 1992 and was a repairman for the Hawk missile system before switching jobs to become one of the Army’s psychological operations specialists, according to the defence official.

So-called “Psy-Ops” specialists are responsible for the analysis, development and distribution of intelligence used for information and psychological effect; they research and analyse methods of influencing foreign populations.

Joseph Rackley of North Carolina said Page lived with his son for about six months last year in a house on Mr Rackley’s property. Wade was bald and had tattoos all over his arms.

”I’m not a nosy kind of guy,” Mr Rackley said. “When he stayed with my son, I don’t even know if Wade played music. But my son plays alternative music, and periodically I’d have to call them because I could hear more than I wanted to hear.”