The gunman Wade Michael Page's former girlfriend Misty Cook, a waitress and nursing student with reported ties to white supremacist organisations, was arrested as part of a joint investigation between the FBI and South Milwaukee Police Department “on the crime of felon in possession of a firearm.”
“Charges (against her) will be sought through the Milwaukee County District Attorney's Office,” Milwaukee police said in a statement after the arrest of 31-year-old Cook.
A federal law enforcement official was quoted as saying by ABC News that Cook was held on the grounds that she is prohibited from having a gun as a convicted felon. She was charged in 2002 for fleeing and eluding a traffic officer.
Cook's relationship with 41-year-old Page, who was killed by police after he gunned down six Sikhs in the gurdwara on Sunday, fell apart in weeks leading up to his shooting spree.
Though police recovered a gun from Cook's residence during a search operation, law enforcement officials said that the weapon was not involved in the shooting incident.
Cook had lived with Page at two separate apartments in South Miliwakee.
Federal agencies were, meanwhile, clueless of what prompted the former soldier's rampage and fear that the motive may have died with him.
With Page, an army veteran, dead, the investigators warn that that the motive may never be known.
“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,” Oak Creek Police Chief John Edwards was quoted by CNN as saying.
Although detectives are following up leads in several states, law experts quoted by the media feel that their findings might never be presented in court.
At the moment investigators are sifting through the life of Page, assembling the biodata of a man who apparently had few relatives and friends, a patchy work life and a thin criminal record.
The federal investigators and the police detectives are also collecting data about the white supremacist to get to the bottom of what motivated him to carry out the gruesome act.
But they are apprehensive whether the full story behind the attack will ever be known.
The FBI has taken over the case but released little official information.
In sketchy details, the fragments of Page's past that have emerged suggest that he lived a troubled life.
Police are following the leads whether Page held a personal grudge against the Sikhs or was he motivated by racist ideology, that could lead investigators to collect intelligence on white supremacist groups to prevent future such attacks.
CNN quoted Sikh groups in US as fearing that though Page may be dead other white supremacist and ‘neo-nazi' groups could harbour similar intentions.
In Oak Creek, Wisconsin, thousands of people gathered last evening in an outpour of support for victims of the shooting. They lit candles, flew orange Sikh flags and joined in Sikh prayers.
“What we learned, you know, about the shooter is he did stuff with music that was completely full of hate and energy that was brain-washing to himself,” Amardeep Kaleka, whose father Satwant Singh Kaleka was president of the gurdwara and among those shot and killed, said.