As more details emerged about the Wisconsin Gurudwara slayer's 'neo-Nazi' leanings, the American Federal Bureau of Investigation on Tuesday intensified its probe into his links to white supremacists to ascertain the motive that spurred the former soldier to unleash his hatred on Sikh worshippers.
Wade Michael Page's neighbours said he rarely left his one-bedroom house where he lived alone, and never made eye contact, but civil organisations which monitored his actions, described the 40-year-old as a "frustrated neo-Nazi" who had been leader of a racist white-power band.
The FBI said they were looking into Page's ties to white supremacist groups but insisted there were no prior warning signals that could have led investigators to believe he was plotting something so vicious.
Special Agent Teresa Carlson, head of the Federal Bureau of Investigation's Milwaukee office, said the gunman was the subject of a "domestic terrorism" probe.
The FBI also ruled out the involvement of a second person in the Sunday shooting, hours after releasing the picture of a "person of interest".
Officials cleared the man after interviewing him and affirmed that the slaying was the handiwork of a lone gunman.
"The unidentified subject has been located, interviewed and does not appear to be connected with the shooting incident at Oak Creek," a FBI spokesman told PTI.
Earlier on Monday at a news conference, the FBI said they were trying to identify a suspicious man who arrived at the scene after the shooting and released a photograph of him, asking for the public's help.
It emerged from disconnected pieces of information that the ex-army veteran regularly attended hate events, was an ardent believer in the white supremacist movement and was associated with rock bands whose violent music talked about murdering Jews and black people.
He played in white supremacist heavy metal bands with names such as 'Definite Hate' and 'End Apathy'. Director of Southern Poverty Law Center's intelligence project Heidi Beirich told the Milwaukee-Wisconsin Journal Sentinel that her group had been tracking Page since 2000, when he tried to purchase goods from well-known hate group National Alliance.
She said her centre, which had studied hate crimes for decades, had evidence that Page attended "hate events" around the country.
Page had once said in a 2010 interview posted on the website of the record company Label56 that his music was about "how the value of human life has been degraded by tyranny."
Mark Potok, a senior fellow at the Southern Poverty Law Centre said in a New York Times report that the music that comes from the kind of bands Page was affiliated with is "incredibly violent, and it talks about murdering Jews, black people, gay people and a whole host of other enemies."
In the interview posted Label56's website, Page talks about going to an annual white-supremacist festival 'Hammerfest' and said he played in various neo-Nazi bands, including 'Blue Eyed Devils'.
One of the songs by the band includes the lines, 'Now I'll fight for my race and nation/Sieg Heil!'
Another song by a band that Page played had words like "our race war" and "What has happened to America/That was once so white and free."
According to SITE Monitoring Service which follows white supremacist trends, Page had an extensive presence on Hammerskin and other white nationalist websites.
Reacting to the incident that came two weeks after a shooting rampage at a movei theatre in Colarado, US President Barack Obama expressed concern over the recurring pattern of violence and asked Americans to do some "soul-searching".
"I think it will be very important for us to reaffirm once again that, in this country, regardless of what we look like, where we come from, who we worship, we are all one people, and we look after one another and we respect one another," he said.