AURORA -- It's been three weeks since five people were shot and killed at the Henry Pratt factory in Aurora.
Friday, one of the survivors, Timothy Williams, is suing the Illinois State Police because of the shooting.
He claims it's the State Police Department is at fault for allowing the shooter to buy a gun.
Williams was shot three times during the Aurora mass shooting and is now suing Illinois State Police for $2-million, claiming the gunman would have never had a weapon if state police did their job correctly.
In a lawsuit filed Friday morning, Williams, who worked as a union steward at Henry Pratt Manufacturing, said Illinois State Police conducted inadequate background checks on the gunman, Gary martin, which allowed him to buy a gun.
The legal team said state police missed Martin's violent criminal history when the department issued him a firearms owners ID card - or a FOID card.
Officials said Martin used that gun to shoot and kill five people and injure six others during the Aurora mass shooting last month.
According to court documents, Martin had a long criminal history, including a felony conviction for beating his girlfriend with a baseball bat and then stabbing her with a kitchen knife.
Although Martin's conviction was discovered when he later applied for a concealed carry license, the lawsuit claims state police did not do enough to retrieve the gun after the mistake was discovered in 2014.
"The state police have claimed they revoked the FOID card and weapons but the file they produced does not say that," Attorney David Rapoport said. "If Illinois State Police had done their due diligence, no lives would have been lost."
Illinois State Police said they cannot comment on pending litigation.
Williams is still recovering at home.
His lawyers said he is not sure if or when he may be able to work again.
Aurora mass shooting victim sues Illinois State Police