An argument during a Halloween event at a Long Beach elementary school ended with one teenage boy hospitalized and another arrested, according to police.

The attack happened at about 5:50 p.m. Friday on the campus of Lafayette Elementary School at 2445 Chestnut Avenue, according to the Long Beach Police Department.

Two 14-year-old boys had gotten into an argument, “which escalated when the suspect stabbed the victim,” police said in a statement on their website.

Medics from the Long Beach Fire Department took the wounded boy to the hospital. Police said he’d been stabbed in the upper body, but the wounds weren’t life-threatening.

Officers arrested the other boy on suspicion of “assault-related charges,” police said.

Police said they are still investigating.

Editor’s note: This story was updated to correct the day of the attack.