The shooting happened at approximately 12:30 a.m. at the Ultra Lounge in the 2100-block of North Milwaukee when, police say, a fight of some sort broke out.
Four men were hit by the bullets, but none of them was seriously hurt. A 26-year-old man was shot in the side, a 24-year-old man was shot in the leg, a 29-year-old man was shot in the thigh and a 33-year-old man was shot in the arm, side and leg, said police News Affairs Officer Ronald Gaines.
Three of the men were taken to Advocate Illinois Masonic Medical Center, Gaines said, and the fourth man was taken to Saints Mary and Elizabeth Medical Center.
An Ultra Lounge manager, who asked not to be named, said the shooting happened during a private party featuring hip-hop performers.
The manager said the bar was busy and had extra security guards for the party. The atmosphere was relaxed, she said, and people seemed to be having a good time until the shooting happened.
"It's really disappointing because we've worked very hard to change this bar and offer continuity with what is in the neighborhood," the manager said. "The energy was positive ? There was nothing that indicated this would happen."
Yellow and red crime scene tape sectioned off the bar and a nearby parking lot as Area North detectives collected details. Investigators searched a minivan and a black sedan parked in the northbound lanes of Milwaukee Avenue.
Police had made no arrests in connection to the shooting later Wednesday morning.
(The Sun-Times Media Wire contributed to this report).