Nearly two dozen people were injured early Sunday when gunfire erupted at an "Art All Night" event in Trenton, New Jersey as a fight between a group of suspects escalated into a shooting, which in turn triggered a stampede. The incident left one suspect dead, and police are investigating whether anybody else was involved, according to Fox News. A second suspect is in custody.

Mercer County Prosecutor Angelo J. Onofri said that 20 people were injured i the shooting, 16 of whom were treated for gunshot wounds at nearby hospitals.

"It's a massive crime scene."

The gunfire, which involved "multiple individuals", broke out shortly before 2:45 am at the 24-hour "Art All Night" show in the Roebling Market section of the city, according to Onofri.

"This is truly a tragedy for Trenton," Trenton Mayor Eric Jackson said.

The event began Saturday afternoon and was scheduled to continue until Sunday afternoon and typically draws thousands of people. The festival showcases local art, music and food.

Four people are listed as in critical condition, while a 13-year-old boy is listed as in "extremely critical condition."

Two suspects have been identified: One, a 33-year-old man, was pronounced dead at the scene - though it's unclear if the suspect was shot and killed by someone else or by police. The other was taken into custody by police. Police are investigating whether the suspect was shot and killed by another patron, or by police. Trenton police at the scene told local media that officers engaged with at least one gunman. Multiple weapons were discovered at the scene, and police are still combing through a warehouse where the first shots rang out.

One witness said they saw two individuals throw punches at each other before the gunshots were fired. "I saw two punches and then heard several gunshots," Franco Roberts said.

Roberts told the newspaper he thought something bad was going to happen because there were "more people outside than in the warehouse" just standing around.

"Everybody ran toward the door," he said. "And the people fighting and shooting got mixed with the crowd that was running and they went out the door shooting."

Two witnesses describe standing outside the warehouse talking when they heard what sounded like fireworks.

"And all of a sudden, my brother goes to me, 'You hear that gunfire?' I go, 'It sounds like fireworks.' He said, 'No, that's gunfire.' Next thing you know, we turn around and everybody's running down the street. All hell broke loose," Nicolo said.

One resident said he saw police helping a man who'd been shot in the leg.

"I saw two police officers escort a guy that got shot in the leg; they bandaged him up and whisked him away before the ambulance came here," he told WPVI. "It was pretty gnarly."

In the aftermath of the shooting, witnesses said Trenton's Roebling Market parking lot was covered in trash, broken glass and liquor bottles.