A stabbing at an Arizona high school left one student dead and another charged with second-degree murder.

Chris Aguilar, 16, is accused of fatally stabbing Michael Montoya II, 16, inside their classroom at Maryvale High School in Phoenix earlier this week, The Arizona Republic reported.

Phoenix police and school security responded on Tuesday to reports of a stabbing at the school just before 11 a.m. and found a boy, later identified by police as Montoya, with multiple stab wounds.

He was taken to St. Joseph’s Hospital, where he was pronounced dead at noon, according to court documents obtained by the newspaper.

Authorities detained Aguilar at the school before he was taken to Maryvale Hospital to treat a cut on his right hand. A school resource officer found a 4-inch folding knife that had Aguilar’s name etched into the handle.

Several teens told police that Montoya had robbed Aguilar of a gun — and that Aguilar and his twin brother were talking about killing Montoya after the alleged robbery, according to the report.

Two teachers who witnessed the stabbing told authorities that Aguilar was the aggressor. They also said Montoya was unable to defend himself, according to the court documents. Both teachers and students witnessed the fatal attack, according to the report.

One of their classmates told police that Aguilar usually sat behind her in class, but instead he sat next to Montoya and started punching him. The witness said she saw Aguilar take out his knife and stab Montoya three times, according to the court documents.

Another witness told police that Montoya tried to run away but fell as Aguilar attacked him. Aguilar immediately ran out of the classroom after the stabbing. The teenage suspect dropped the knife outside the classroom, according to witnesses.

That same person told police they used Montoya’s cellphone to call 911, according to the documents.

Students at Maryvale High School were sent home early after the stabbing, and classes were canceled on Wednesday.

“The district’s investigation is ongoing and we continue to cooperate fully with the police investigation, a piece of which includes how the weapon got onto the Maryvale campus,” district officials told local media including AZFamily. “We do not have any further comment at this time.”

After Aguilar was released from the hospital, he was booked into a Maricopa County jail on a second-degree murder charge. He is being held on a $500,000 cash-only bond.

Under Arizona law, juveniles between the ages of 15 and 17 are tried as adults if they are charged with murder or a violent felony. Aguilar is scheduled to appear next in court on August 26.