One person was killed and at least 15 others were wounded after several people got into an altercation and at least one of them opened fire at a nightclub in Cincinnati, police said.
The shooting happened at 1 a.m. ET Sunday at the Cameo Nightclub on Kellogg Avenue, authorities said.
Despite the large number of wounded, police told NBC News that there was no indication that the bloody attack, which happened inside the venue as hundreds of people partied, was related to terrorism. The assailants were still at large Monday morning.
"The conflict is believed to have begun between specific groups or individuals earlier in the day, escalating and ultimately leading to this tragedy occurring at the nightclub," Cincinnati City Manager Harry Black said early Sunday.
At a news conference later, Cincinnati Police Chief Eliot Isaac said it appeared that "several local men got into some type of dispute inside the bar and it escalated into shots' being fired from several individuals."
One person was killed, and at least 15 others were injured, Isaac said, with one of the injured in "extremely critical condition" and several others suffering serious injuries.
He also identified the dead man as Obryan Spikes, 27. Cincinnati Police Capt. Kimberly Williams said officers tried cardiopulmonary resuscitation but were unsuccessful.
The University of Cincinnati Medical Center said Monday morning that five patients remained hospitalized, with two in critical condition and three in stable condition.
Cincinnati Mayor John Cranley reiterated that the shooting wasn't terrorism-related, but he said: "To the victims, what difference does that make? They've been terrorized by gun violence — innocent victims."
"People were just going to have a good time and ended up getting shot. That is totally unacceptable," he said.
Cranley said he got a phone call from Ohio Gov. John Kasich, who had expressed his condolences.
Emergency call logs seen by NBC News indicated that a caller told emergency services at about 1:30 a.m. that a man had been shot in the head but was still breathing.
Assistant Police Chief Paul Neudigate told NBC affiliate WLWT that several other victims had life-threatening injuries.
"We are in the middle of a very horrific situation that occurred at the nightclub with multiple victims," Neudigate said. "It's going to be a long night for our homicide units to investigate."
Neudigate added that hundreds of people were inside the club, calling it a "chaotic crime scene."
"Many of them fled, unfortunately. Many of the witnesses fled, but everyone that we can identify is being interviewed," he said.
Neudigate said the attack was one of the largest shooting cases he has worked on in his 20-plus years with the department.
Kelly Martin of the University of Cincinnati Medical Center confirmed to NBC News that the hospital received eight patients.
She said one patient was in a critical condition, three patients were in a serious condition and four patients were stable.