RCMP say they were advised by the local school board that Ponoka Composite High School was in lockdown while steps were taken to locate the student.
Officers found a 17-year-old boy at his home in Ponoka and arrested him.
They say ammunition and firearms — including a .22-calibre rifle and a high-powered rifle — were found.
Charges are pending for uttering threats, unsafe storage of firearms and possession of weapons dangerous to public peace.
A tentative court date has been scheduled for Dec. 28.