During search operation, the police recovered a gun from the residence of Misty M Cook, the ex-girlfriend of Wade Michael Page, 41, who allegedly went on a shooting rampage inside the gurdwara on Sunday in Wisconsin killing six people. He was shot dead by the security officers.
While law enforcement officials said that the weapon recovered from the residence of Cook, 31, was not involved in the shooting incident, Fox News quoting officials said on Tuesday that Cook has a prior felony conviction.
"But it was unclear if that was the reason for the new charge or if there was some other reason that the gun was deemed illegal. No details about the past conviction were available," the news channel said.
A nursing student, Cook lived with Page at two separate apartments in South Miliwakee. So far she has not been charged in the shooting incident.
However, she is likely to be arrested and processed by the South Milwaukee Police Department, the news channel said.
Jenna Benn, the Anti-Defamation League's assistant regional director in Chicago told Stars and Stripes that Cook is affiliated with the white-power group Volksfront and is a supporter of the Hammerskin Nation, a Dallas-based white supremacy group.
She said the suspected gunman's ex-girlfriend is a prolific poster on hate forums.
While Cook refused to give interviews, her neighbours told Fox news that Cook and Page separated recently.
One neighbor recently reported hearing Page "banging on the door of his old apartment, demanding to be let in."
David Brown, 62, a Navy veteran who also lived in the building, said Page often lifted weights in the basement, as angry music blasted away.
He said Cook began to change after living with Page.
"The longer she stayed here with him, the more quiet and more withdrawn she got," Brown told FoxNews.com.
"In the end she didn't even make eye contact with me," Brown was quoted as saying by Fox News.
According to the news channel, neighbors who lived in the building where Page and Cook shared a home for the first four months of 2012 said they were a strange couple, keeping to themselves.
They played ear-splitting rock music and barely acknowledged neighbors, they told FoxNews.com.
"He wouldn't even look at you," said Robert Haugle, 31.
When a Hispanic family moved into the building, the couple moved out.
"They had no stuff, and they didn't have movers, it was really weird," Haugle added.
"Just one day they were gone," he told the news channel.