Wow, I grew up near there, have family in the area. Doubt I’d know anyone involved but dang... I went to chess tournaments at that high school.
Seconding the description of the area as white, upper-middle-class.
WTAE confirming that IT WAS A KNIFE.
Perp is a student. In police custody.
Another ambulance being shown at HS front doors (one just left about ( mins ago).