Well, he was thrown off the Community College campus by campus cops, and refused reentry until he produced a doctor's report. That's a type of Restraining Order, and if it were properly reported, would have prevented him from buying the Glock.
If the laws on the books were properly enforced, there would not be a demand for new laws now.
Sounds like he was forced off the property. Not a court ordered restraining order.
I know you want to blame this on somebody or something, but sometimes people slip through the cracks and their first real incident is a big one. Did he maybe lie about smoking marijuana on his ATF app? Maybe. But I don't think we can surmise anything else. We can't start throwing odd people into mental hospitals or half of us on FR would be there for the way we think.
It's the inherent risk in a free society. The solution? Arm yourself.