It happened around 8:30 p.m. Thursday on the concourse inside the CURE Insurance Arena on Hamilton Avenue.
The stabbing happened during the Mercer County Final game between Trenton and Notre Dame high schools.
Investigators say the stabbing occurred after the game ended and no players were present.
According to the Mercer County Prosecutor's Office, 23-year-old Khalil Glanton, of Trenton, was stabbed multiple times inside the arena.
He was taken to Capital Health Regional Medical Center where he was pronounced dead.
Trenton Public School District Superintendent James Earle said in a statement that Glanton was a 2019 graduate of Trenton Central High School.
"At this time, we are not aware of any current students who may have been directly involved but have contacted those who may be connected to ensure they are not on campus today (Feb. 17)," Earle's statement reads.
The superintendent went on to say that administrators have activated the district crisis team for students and staff who may need support.
"Additional law enforcement will be present inside TCHS and patrolling the school campus as a precaution," Earle said.
Students were stunned by what happened.
"It's a real shock, to be honest. I never could expect it to happen," said Edward Bachiller, a sophomore at Trenton Central High School.
No further information was available on Friday regarding what sparked the stabbing.
"At a time when we should be celebrating the achievements of our basketball team winning the county championship at Cure Arena, we are instead confronted with acts by individuals whose main goal seems it was to commit violence," said Trenton Mayor Reed Gusciora.
The stabbing has raised questions about the security measures in place at Cure Arena, which is a county facility.
"I'm also calling for an independent investigation by the county regarding the overall security breaches that happened - if they did - at the arena," said Gusciora.
No arrests have been made.
Anyone with information is asked to contact the Mercer County Homicide Task Force at (609) 989-6406.