AN ALL-NIGHT ARTS and music festival in New Jersey was targetted in a gun attack this morning, injuring dozens of people and leaving four in a critical condition.

Authorities said that 22 people were injured and one of two suspects died after the crowd were sprayed with gunfire.

Seventeen people were treated for gunshot wounds, said Mercer County Prosecutor Angelo Onofri. Four of those, including a 13-year-old boy, remain in critical condition.

Two suspects opened fire around 2.45am during the Art All Night Trenton festival that showcases local art, music, food and films.

One of the suspects, a 33-year-old man, was killed, authorities said. Onofri said he believes police killed him. Another suspect is in custody. Onofri said “neighbourhood beef” is behind the shooting inside the historic Roebling Wire Works Building.

Crime scene tape surrounded the site of the old warehouse that now shares a parking lot with a supermarket, bank and laundry facility.

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

Gennie Darisme was at the festival when the shooting occurred, getting ready to leave around 2.45am 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 ceased, Darisme said she saw someone bleeding on the ground, in handcuffs.

“People were running to him, trying to see his face, to see if he’s a family member or a friend,” she said.

Ernie Rivas has owned a shop near the site of the shooting for 17 years and said he came back from the beach this morning when he heard what happened.

“I’ve never seen this happen. It’s bad, I feel bad, especially on Father’s Day,” Rivas said.

Theresa Brown said she’s been volunteering at Art All Night for 12 years and has never seen or heard of violence like this. She said she was leaving her volunteer shift around 2am and heard “pop, pop, pop”.

“I thought it was a car backfiring,” she said.

She returned to the scene around 7am and saw the police.

Art All Night Trenton began Saturday afternoon and was scheduled to conclude this afternoon. The remainder of the festival has been cancelled.

“We’re very shocked. We’re deeply saddened,” festival organisers posted on social media.

Our hearts ache and our eyes are blurry but our dedication and resolve to building a better Trenton through community, creativity and inspiration will never fade. Not tonight. Not ever.

A spokeswoman for St Francis Medical Center in Trenton said 10 victims were being treated there for minor injuries. She said they were both men and women, ranging in age from 17 to 48. They were in various stages of being released, she said.

One man with a gunshot wound was transferred to Cooper University Hospital in Camden.

Capital Health Systems spokeswoman Kate Stier said they have “at least 16″ patients there, including the 13-year-old boy in critical condition. That total may not include people treated and released.

Trenton Mayor Eric E Jackson said the violence can’t be “discarded as just random violence; this is a public health issue”.