A 16-year-old high school student in Arizona has been arrested for allegedly killing a classmate, fatally stabbing the other teen with a pocketknife during a fight on campus.

Chris D. Aguilar was taken into custody on Tuesday and charged with one count of second-degree murder in the slaying of 16-year-old Michael Montoya II, authorities announced.

According to a news release from the Phoenix Police Department, officers at about 10:54 a.m. on Tuesday responded to Maryvale High School in the 3400 block of N 59th Avenue after a school staffer reported that an assault had taken place “inside one of the classrooms.” Upon arriving at the scene, the first responding officer was directed to the school’s administration building where he detained the accused assailant, later identified as Aguilar.

Emergency medical personnel and additional officers on the scene located the victim, later identified as Montoya, who appeared to be suffering from multiple stab wounds. The victim received brief treatment at the school before being rushed to a local hospital. Montoya succumbed to his injuries and was pronounced dead shortly after arriving at the facility.

Following Aguilar’s arrest, detectives said they “made progress in their initial investigation by interviewing multiple witnesses and reviewing video.”

The investigation allegedly revealed that Montoya “was attacked while in class by another male classmate who was armed with a folding pocketknife, believed to have been brought onto campus,” the release states. “After the attack, the suspect ran out of the classroom and dropped the knife. He was seen by security staff bleeding from his hand and was placed into custody. Both Montoya and the suspect were taken to separate 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.