Two men arrested in connection with a weekend shooting that wounded nine people inside a Cincinnati nightclub face federal charges, the U.S. Attorney’s Office for the southern district of Ohio said Tuesday. Prosecutors said the men, identified as Franeek Cobb, 24, and Derrick Long, 29, are being charged in federal court for illegally possessing a firearm or ammunition as individuals previously convicted of a felony.

Federal prosecutors said surveillance footage from Riverfront Live, where the shooting took place, shows both Cobb and Long firing weapons early Sunday morning. According to an affidavit described by prosecutors, Cobb observed Long inside the venue, pulled out a firearm and began firing at him, while Long fell to the ground and then allegedly began firing at Cobb.

The attorney’s office said ballistic evidence collected from the scene showed only two firearms were discharged during the shooting. U.S. Attorney Dominick S. Gerace II said in a statement that the federal case focuses on protecting communities and holding accountable people who threaten others through illegal violence or unlawful firearm and ammunition possession.

Cobb was arraigned Tuesday in Hamilton County Municipal Court on local charges of felonious assault related to the incident. During the arraignment, Hamilton County Assistant Prosecutor Connor Wood said Cobb had a “long-standing grudge” against an unidentified victim in the case and, Wood said, Cobb “immediately” opened fire after seeing the victim inside the venue. Wood said there was “no interaction between the parties leading up to this.”

Long, who also faces local charges in the shooting, did not appear in court Tuesday. Court records described allegations that Long “knowingly possessed and discharged a firearm” at Riverfront Live, where several people were injured, and records did not list an attorney for Long at the time.

Prosecutors said the shooting happened around 1 a.m. Sunday at Riverfront Live along the Ohio River in the city’s east end. Police responding to reports of gunfire found nine people with gunshot wounds, and officials said all were taken to hospitals and were in stable condition.

The gunfire erupted during a birthday celebration hosted by Jermaine Tandy, also known as DJ Fresh, according to a post on Tandy’s Facebook page. Management representing Tandy said in a statement it was “devastated” by the violence and called it a “senseless act,” according to prosecutors’ summary of the statement.

Witness Anton Canady told The Associated Press that he heard what sounded like a fight before shots rang out, and that as people rushed toward exits, his girlfriend fell. Canady said he laid on top of her to prevent her from being trampled. After he got outside, Canady said he learned his cousin was among those shot, and that he used cloth from a nearby car to apply pressure to her wounds until first responders arrived; Canady said he later spoke with his cousin and that she was “doing good” but in shock.

The Cincinnati Police Department homicide unit, the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives are working together on the investigation. The AP reported that while the Cincinnati shooting happened almost simultaneously with a deadly bar shooting in Austin, Texas, an ATF spokesperson said earlier this week it was not believed to be an act of terrorism.