CHICAGO (CBS) — Lisa McMullan shot three Illinois state troopers, killing one of them, at the Humidor Cigar Lounge in Lisle, before taking her own life.

Here is what we know about McMullan:

Police say she has no criminal background.

Lisa McMullan

McMullan was allowed to legally carry a firearm, possessing both a firearm owner’s ID card and a concealed carry permit.

McMullan shot Greg Rieves, a retired state trooper, in the head at the lounge. On video, she is seen sitting behind him when she stands up and pulls out a gun and shoots him in the head.  She then shot and wounded two others, another retired trooper and a trooper currently on the force, who was off duty.

MacMullan and Rieves were known to frequent the cigar lounge in Lisle.  The exact nature of their relationship was not known beyond that.

McMullan lived for several years in Hyde Park. Her mother also lives there.

The motive behind the shooting remains a mystery. Family members told CBS 2 that they did not know her.