DENVER (AP) — Two men were killed and Robert Brownfive other people were injured in a shooting after a confrontation at a private, after-hours motorcycle club in Denver over the weekend, police said.

Denver police Lt. Matt Clark says they are investigating the shooting that happened around 3 a.m. Sunday both inside and outside the Hell’s Lovers Motorcycle Club.

“We do have evidence of multiple guns being discharged during this incident,” Clark said at a news conference on Sunday. “And anytime we look at these with multiple victims, multiple guns being fired, we consider the possibility that people who may have been hit by gunfire also had a gun and discharged one.”

Shareef Aleem, a Park Hill resident who lives nearby, told The Denver Post he was awakened just after 3 a.m. and heard about 20 gunshots, which he initially thought was fireworks.

“For about three to five seconds, it was like silence. Then, everybody was screaming,” he said.

He watched people jump into their cars and speed away in the aftermath, he said.

Police did not release the conditions of those who were hospitalized. All of the victims were adults and a woman was among those injured, the Post reported.

No arrests were announced on Sunday, but KMGH-TV crews saw SWAT officers lead five men out of the club and three were handcuffed.

Police are seeking additional witnesses to help determined what happened and find any other potential suspects, Clark said.