Twenty people have been injured, some critically, in a shooting at an arts festival in Trenton, New Jersey on Sunday. One person, suspected to be behind the shooting, has been killed according to local officials.

A second suspect is in police custody, according to Mercer County Prosecutor’s office. Fifteen of those injured suffered gunshot wounds and a 13 year-old boy is among the casualties.

Local authorities say that several people opened fire inside the venue and multiple weapons were recovered in the scene. The casualties were confirmed by the Mercer County Prosecutor’s office.

Police received reports that a man had opened fire inside Roebling Market, where the all-night event took place, shortly before 3 am.

"It's a massive crime scene," Mercer County Prosecutor Angelo J. Onofri said at a news conference.

Trenton Mayor Eric Jackson described the incident as “truly a tragedy,” and expressed his sympathies to the victims and their families.

One eyewitness told WPVI that he saw a person with gunshot wounds. “I saw two police officers escort a guy that got shot in the leg,” he said. “They bandaged him up and whisked him away before the ambulance came here."

The 24-hour arts festival, which included artwork submitted by local children, and an anti-gun violence project, has since been cancelled.

@aantrenton It’s with great regret that we announce that the remainder of Art All Night has been cancelled due to a tragic incident that occurred overnight. We’re still processing much of this and we don’t have many answers at... https://www.facebook.com/aantrenton/posts/

@kpgoing4change “Imagine a world free of gun violence. What do you see?” Making art and talking about Moms Demand Action at Art All Night - Trenton. 24 hour event tabling! @momsdemand @aantrenton

@cosmic_hiccup Replying to @TheScottCharles This is what our community art project looked like when my daughter and I left at 11:30.