An Arizona teenager is facing felony charges after showing up at school with an AR-15 semi-automatic rifle and a cache of ammunition stashed in his lunchbox, according to reports.

The 15-year-old student, who was not identified, forced Bostrom High School in Phoenix into a lockdown around 1 p.m. Friday after administrators got a tip that the weapon was on school grounds, NBC News reported Saturday.

Police responded to the campus, confiscated the weapon and took the student into custody.

The teen was charged as a juvenile with possession of a weapon, carrying a weapon on school grounds and interfering with an educational institution.

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

In a separate statement school district officials also thanked the unidentified tipster.

“As always, the safety and well-being of our staff, students and visitors remains our top priority and we will work with law enforcement as they continue to investigate,” the statement said.

AR-15-style rifles have been identified as the weapons used in many of the recent mass shootings in the US, including the mass shooting at a Texas mall earlier this month that left eight dead and last year’s school massacre in Uvalde, Texas, that killed 19 people, including students.