This sounds as though he was just moving through the area of the tragedy, thinking about that horrible day.
No, he should not have been back there, and was told to stay away from that area, which is probably still roped off from the rest of the campus. It doesn’t sound like he had any ill intent.
If someone really wants to help this kid, they should encourage him to enroll in a different school, in a different state, and maybe even under a different name.
It doesn’t help that his photo his widely published, but it’s not too late to give him a chance to leave this place behind for a decade or two. Too many reminders.
Very good points you two brought up in your comments. Thanks!