[Puppage]

I bet the gun belonged to one of his parents...

What makes you say that?

[eastforker]

Availability. Most 15 year olds don't buy guns, even illegal ones off the street. And by illegal I mean the sale there of not the gun itself. Most all reports of kids with guns at school was that the gun belonged to a parent or other close relative.

[Rakkasan1]

...or stolen
...or one of his friend's
...or bought on the street
hey, at least he wasn't having sex with his teacher.
(that we know of)