The suspect in the Wisconsin Sikh temple tragedy is dead and can never be questioned about his motives, but authorities have arrested Wade Michael Page's former girlfriend on a weapons charge.
Misty Cook was charged with possessing a gun, which is illegal because she is a felon, said South Milwaukee Police Lt. Jason Walker.
The arrest was part of a joint investigation between the FBI and the South Milwaukee Police Department, Walker said.
Walker released no other details and did not comment on whether Cook had any connection to Sunday's shootings at the suburban Milwaukee gurdwara, the Sikh house of worship, that left six people dead.
The FBI scheduled a news conference for 11 a.m. Wednesday in Milwaukee to provide an update on the shooting investigation.
Page, a 40-year-old Army veteran who neighbors say played in a so-called hate-rock band, was the lone gunman in the rampage at the temple, police said. He was shot to death by police responding to the attack in Oak Creek.
The investigation continued as a community reeled from the carnage.
For a third consecutive night, mourners held a vigil Tuesday night to remember the dead, pray for the wounded and grapple with the grief.
They lit candles in a park and stood together in solidarity. Many hoped for answers as to why anyone would shoot their way into a house of God.
Police have not identified a motive, found any telltale writings or any clues left by the gunman.
Page's family members have not reported observing any warning signs, said Oak Creek Police Chief John Edwards.
Authorities received tips that Page might have links to the white supremacist movement, but nothing has been confirmed, according to Edwards and the FBI.
White supremacist groups still strong
"We may end up with just a lot of facts on what he is involved with, who he may be associated with, but we may never know that motive, because he died, and that motive died with him," Edwards told CNN's "The Situation Room."
The chief also said, counter to initial witness statements, Page did not have a 9/11 tattoo.
While the FBI has said Page never was the subject of an investigation, he was mentioned in a small number of federal law enforcement reference files in cases going back seven years, a law enforcement official told CNN Tuesday.
The official said there is no information to suggest that investigators wanted to open a case on Page but did not have the evidence to justify it. Page might have been sympathetic to a certain ideology, but there was no evidence he had committed a federal crime prior to the Wisconsin shooting, the official said.
The official did not provide details about the nature of the cases in which Page's name was mentioned.
Bernard Zapor -- the Bureau of Alcohol, Tobacco, Firearms and Explosives special agent in the investigation -- said Monday that the 9mm semiautomatic handgun with multiple ammunition magazines used by the attacker had been legally purchased.
Page bought the gun July 28 at the Shooters Shop in West Allis, Wisconsin, and picked it up two days later. He also bought ammunition there and used the shop's range.
Shop manager Eric Grabowski and owner Kevin Nugent told CNN Tuesday that surveillance video of Page buying the gun and using it in the range two days later has been turned over to investigators. The suspect did not exhibit unusual behavior while in the store, Grabowski said.
The magazine for the handgun holds at least 17 bullets.
Explainer: Who are the Sikhs?
According to a man who described himself as Page's old Army buddy, the attacker talked about "racial holy war" when they served together in the 1990s. Christopher Robillard of Oregon, who said he lost contact with Page more than a decade ago, added that when Page would rant, "it would be about mostly any non-white person."
Page, born on Veterans Day in 1971, joined the Army in 1992 and left the service in 1998, according to Army spokesman George Wright. Page's service was marked by "patterns of misconduct" and he received a general discharge due to "discreditable incidents," according to a Pentagon official. Robillard said Page was pushed out for showing up to formation drunk.
John Tew, manager of a Harley-Davidson motorcyle store in Fayetteville, North Carolina, told CNN he fired Page from his parts coordinator job in 2004 because Page "had a big problem with authority" and with working with women. Tew said he found an application for the Ku Klux Klan on Page's desk the day he was dismissed.
Pete Simi, a University of Nebraska at Omaha professor said he knew Page while doing research on extremist groups about 10 years ago.
Page told him he started identifying with neo-Nazis during his time in the military. The former soldier told him he believed the deck was stacked against whites, Simi said, adding he believed Page drank excessively.
Two neighbors of Page identified him in photos that showed him playing in the far-right punk band "End Apathy" with Nazi flags hanging near him.
The gunman's former stepmother spoke of a very different Wade Page she once knew before losing touch with him more than a decade ago, when she and Page's father divorced.
"It's like I don't even know that person," Laura Page said of more recent photos of Page. "It is not someone I ever could possibly know or be associated with." She told CNN that the Page she knew was gentle and loving and had black and Hispanic friends.
Sunday's attack in Oak Creek occurred 16 days after a gunman killed 12 people and wounded scores at a movie theater in Aurora, Colorado.
The six victims of Sunday's attack were identified by police as five men -- Sita Singh, 41; Ranjit Singh, 49; temple president Satwant Singh Kaleka, 65; Prakash Singh, 39, and Suveg Singh, 84 -- and one woman, 41-year-old Paramjit Kaur.
A wake and visitation are scheduled for Friday morning.