A 16-year-old high school student in Arizona has been apprehended for allegedly murdering a classmate, with the fatal incident involving a pocketknife stabbing during an onsite altercation.

Authorities reported that Chris D. Aguilar was arrested on Tuesday and is facing a charge of second-degree murder for the death of 16-year-old Michael Montoya II.

In a statement released by the Phoenix Police Department, officers responded at approximately 10:54 a.m. on Tuesday to Maryvale High School, located in the 3400 block of N 59th Avenue, after a report of an assault in one of the classrooms. Upon their arrival, the first officer was guided to the school’s administration building where Aguilar was taken into custody.

Emergency responders and additional officers discovered Montoya suffering from several stab injuries. Montoya received preliminary medical attention onsite before being transported to a nearby hospital, where he succumbed to his injuries and was declared deceased shortly after his arrival.

Post-arrest, detectives advanced their investigation through witness interviews and video analysis.

The investigation purportedly showed that Montoya “was attacked by a male classmate in the classroom with a folding pocketknife brought onto the campus,” the statement reports. “After perpetrating the attack, the suspect exited the classroom, leaving the knife behind. Security staff noticed he was bleeding from his hand and detained him. Montoya and the suspect were taken to different hospitals.”

Authorities said they were able to recover the knife used in the attack.

Court documents obtained by local Fox affiliate KSAZ provided additional details about what allegedly took place immediately before the incident.

According to the report, two teachers witnessed the attack, with one of them telling investigators that Aguilar had switched his seat to sit next to Montoya that morning.

“The defendant punched the victim multiple times, then produced a pocketknife from the side of his pants,” police wrote. “This witness observed the defendant stab the victim three times.”

Local CBS affiliate KTVK reported that two days before the fatal stabbing, Montoya had robbed Aguilar of a firearm. After the alleged robbery, Aguilar and his twin brother were reportedly overheard making “statements to murder the victim.”

State Superintendent of Public Instruction Tom Horne issued the following statement in response to the fatal stabbing:

The death of a student as the result of a stabbing at Maryvale High School is a terrible tragedy. Schools must be safe places. The on-campus school safety officer responded immediately, rendered aid to the student, and did his job well. This terrible incident reinforces my commitment to doing everything possible to make schools safe.

KSAZ reported that Aguilar is being charged as an adult. He is currently being held in lieu of $500,000 cash-only bond.