UNITED STATES.- Two gunmen opened fire at an all-night arts and music festival early Sunday morning, sending people running over each other in the scramble to safety, authorities said. One suspect was killed and 22 people were injured.

Of 17 people treated for gunshot wounds, four of them, including a 13-year-old boy, remain in critical condition late Sunday morning, said Mercer County Prosecutor Angelo Onofri.

The shots rang out around 2:45 a.m. during the Art All Night Trenton festival that showcases local art, music, food and films. Onofri said a 33-year-old man was killed, apparently by police, and the second suspect is in custody. He said a“neighborhood beef”is behind the shooting.

On Sunday, crime scene tape surrounded the site of the historic Roebling Wire Works Building that now shares a parking lot with a supermarket, bank and laundry.

Police are also investigating an attempted carjacking that occurred in a nearby alley. Onofri said police are working to determine if it’s connected to the shooting.

Gennie Darisme was getting ready to leave the festival around 2:45 a.m. when she heard shots and saw people running.

“There were people trampling other people, cars hitting other cars,” she said.

When she was walking back to her car after the shots stopped, Darisme said she saw someone bleeding on the ground, in handcuffs.