Wade Michael Page opened fire inside a Sikh temple in the Milwaukee suburb of Oak Creek before being shot dead, police said.
Page, 40, an Army veteran who reportedly played in a far-right punk band, was shot to death by police responding to the Sunday morning attack, Oak Creek Police Chief John Edwards told reporters Monday. He shot several people inside and outside the temple, including a police officer, before being taken out by another police officer with a rifle.
Edwards said certain evidence indicates that the suspect "may have been involved in" a white supremacist movement, but the information remains unconfirmed.
Two neighbors of Page identified him to CNN in photos that showed him playing in the far-right punk band End Apathy. In addition, the nephew of the slain president of the Sikh temple said the attacker had a 9/11 tattoo on his arm, which was one of the first details to come out about the gunman.
While no motive has been established for the slaughter, Teresa Carlson, the FBI special agent in charge of the investigation, said the bureau is looking into whether domestic terrorism -- the use of violence for political or social gain -- played a role.
"We are looking at ties to white supremacist groups," Carlson told a news conference, adding there was no investigation of Page before Sunday's attack.
Sikhs -- who are not Muslims and were historical enemies of Muslims in India -- have been associated in the minds of some Americans with Islam because of their race, beards and turbans, and some were attacked after the Sept. 11 terror atatcks.
"This is something we have been fearing since 9/11, that this kind of incident will take place," Rajwant Singh, chairman of the Sikh Council on Religion and Education in Washington, D.C., told the Associated Press.
"It was a matter of time, because there's so much ignorance and people confuse us [as] being members of Taliban or belonging to [Osama] bin Laden."
Sikh victims killed in the assault ranged in age from 39 to 84, according to a list provided at the news conference.
Two other Sikh victims remained hospitalized in critical condition, while a third was treated and released, Edwards said. In addition, 51-year-old Lt. Brian Murphy was listed as being in critical condition but did not appear to sustain life-threatening injuries.
Page, born on Veterans Day in 1971, joined the Army in 1992 and left the service in 1998, CNN reports. He served as a sergeant, and later as a specialist in the psychological operations unit at Fort Bliss, Texas, in 1994. He was last stationed at Fort Bragg, N.C., attached to the psyops unit, but was dishonorably discharged in 1998 for "patterns of misconduct," a Pentagon official said.
Bernard Zapor, a Bureau of Alcohol, Tobacco, Firearms and Explosives special agent investigating the case, said Monday that the 9mm semiautomatic handgun with multiple ammunition magazines used by the attacker had been legally purchased.
Edwards said a background check on Page revealed he had convictions for drunken driving in Colorado in 1999 and for criminal mischief in Texas in 1994.
Describing Sunday's shooting, the chief said: "They gave the individual commands. He didn't respond to those. He shot some of the squads, damaging them, and he was at that time shot at by one of our officers with a rifle."
When asked about Murphy, the officer shot in the attack, the police chief described the shooting as being "in very close range."
"He was tending to someone down in a crouch position, what it appears," the police chief said. "And the individual [Page] walked up on him, around a vehicle and engaged him very closely - inches to feet, and fired at him. He was shot between eight and nine times."
Witnesses told CNN that Page first opened fire in the parking lot, killing at least one person. He then entered the temple and continued firing, they said.
On Sunday, the FBI and a bomb squad arrived at a home in Cudahy, Wis., near Oak Creek, and ABC News' Milwaukee affiliate WISN reported the action appeared to be related to the temple shootings earlier in the day.
Sunday's attack took place around 10:30 a.m., when temple members were reading scriptures and cooking food in preparation for the main Sunday service and community lunch. The temple has more than 350 members.