Five and a half years, and still no one’s answered this? I find this scenario creepy as hell. Still have my doubts that the person could leave a scene that makes it look like the entire thing was perpetrated by one person than it wasn’t, but out of all the scenarios proposed in this thread, this post creeps me out the most.
I think it’s much the same - possible to get away with it, but unlikely.
You still have to get away without anyone seeing you, nobody can know that you were associated with the dead killer, and you need an alibi when the cops start checking everyone who wasn’t at school that day. And no one better remember you obtaining the guns, which cannot be traced to you in any way. And it is difficult to shoot someone else and make it look like suicide.