Police arrested a student after he allegedly brought an AR-15 and ammunition to a Phoenix high school Friday, authorities said.

The student faces «serious felony charges» after he allegedly brought the semi-automatic rifle, the weapon behind a dozen of the 21 deadliest mass shootings in the US since 2006, to Bostrom High School, where he was arrested. at the main office around 1 p.m. Friday, according to a news release from the Phoenix Police Department.

Authorities also allegedly found more ammunition in the student’s backpack and lunch box, according to the police department.

The student is in custody and the police department’s firearms intelligence unit is investigating along with school and district officials, according to the news release from Phoenix police, who have not publicly identified the student.

“We congratulate those who originally reported the possibility of a weapon on school grounds to the adults on campus who immediately called the police,” a police department statement said.

It was not immediately clear who reported the student to police, how the student obtained the gun and ammunition, exactly what charges he faces, how much prison time he could face if convicted or whether his guardians could face any charges.

A representative for the Phoenix Police Department could not immediately be reached by phone Saturday, and the department did not immediately respond to emailed questions.

NBC affiliate KPNX reported that the student is 15 years old and that the school was closed when the arrest occurred on Friday. NBC News has not independently confirmed those details.

In a statement provided to KPNX, a representative for the school district said: “We are grateful to those who reported this incident to trusted adults. We also thank our staff for working quickly to ensure everyone was safe and the Phoenix Police Department for responding immediately.»

Representatives for the Phoenix Union High School District could not immediately be reached by phone or email on Saturday.

the school district describes Bostrom High School as an «alternative hub» that provides a «small school environment that focuses on student-centered learning while supporting the whole student.»

Arizona does not prohibit semi-automatic riflesbut prohibits minors from buying or possessing a weapon without the written consent of a parent or guardian, according to the Giffords Law Center to Prevent Gun Violence, a nonprofit gun control advocacy group. The state also prohibits firearms on school grounds, except by those authorized to carry them or for use in approved school programs. according to the Giffords Law Center.

The Phoenix incident comes just days after an 18-year-old shooter in New Mexico used three weapons, including an AR-15, to fatally shoot three elderly women: Shirley Voita, 79, Melody Ivie, 73, and her mother Gwendolyn. Schofield, 97 The shooter was killed by police on Monday after his deadly attack.

As mass shootings have increased, calls have intensified to place restrictions on sales of semi-automatic rifles like the AR-15, which was originally created for military use and is now copied by a variety of manufacturers under different names.

With their ability to fire bullets at high velocity, AR-15s are known to inflict heavy damage on the human body and are more likely to be deadly than other firearms.

Washington state banned semi-automatic rifles last month, becoming the ninth state to have such a ban, besides Washington, D.C., according to Associated Press. President Joe Biden has called for a nationwide ban on semi-automatic weapons in light of the rise in mass murder.

jon schuppe and jiachuan-wu contributed.