While this was posted some days ago, I still agree with the school for suspending those students immediately.
Why? For their protection, and the protection of the school.
As an example, let’s say the gunman belonged to a street gang, or had armed friends who got half the story. As well as other kids who are now terrified enough to bring their own guns to school.
So a 72 hour cooling off period sounds like a smashing good idea, as long as it is understood it is without prejudice, that the suspended students will not have it held against them by teachers, etc. It is for their own protection.
It would also be a great idea to have some armed guards at the school, pronto.
If you think about it, the next few days at that school is going to be a wash, anyway, because of gossip & rumor, increased stress, arguments about guns in schools, counseling etc.