At 9 a.m. on a Wednesday, Stafford Township police received a 911 call from an individual claiming she had received an alarming Instagram message from “John Smith,” offering his goodbyes and stating something bad was about to occur.

A minute later, Smith pulled up to the front of Southern Regional High School’s 11/12 building in a black Ford Explorer, exited the vehicle, retrieved a black backpack from the rear, then purposefully walked toward the front door, unloading several rounds from a…