Woman Killed Retired Trooper ‘Without Apparent Provocation’ Before Shooting Self in Ill. Cigar Bar

Illinois police say a 51-year-old woman fatally shot a retired state trooper at a cigar bar and injured two others before fatally shooting herself in the head.

The Friday evening shooting, which occurred at the Humidor of Lisle, was “without apparent provocation,” and surveillance video showed Lisa V. McMullan fatally shoot 51-year-old retired Illinois State Trooper Gregory Rieves in the back of the head, police said.

McMullan was sitting behind Rieves in a media room around 10 p.m. where several people were watching television when she stood up, pulled out a handgun and shot him. She then fired six more rounds, striking 48-year-old off-duty state trooper Kaiton Bullock twice and retired special agent Lloyd Graham, 55, once.

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Rieves was transported to a local hospital where he died. Bullock is in serious but stable condition and Graham remains hospitalized in stable condition.

Police are still trying to figure out the woman’s motive.

“As far as motive, we have some things we think but we have to make sure it checks out before we release the information,” Lisle Acting Police Chief Ron Wilke tells PEOPLE. “We are still interviewing people.”

“We have definitely received information [that] they had some kind of relationship, but what the relationship was we are trying to find out,” he says.

“It is quite horrible,” he says about the shooting.

Wilke says the three men were friends and knew McMullan from the cigar lounge.