This is sounding more and more like a security problem.
Police supposedly on campus. They believe the suspect pulled the alarm to draw people out. So what, he just waltzed in casually and pulled the alarm, and ran back outside and picked up his gun? Does the school not lock the doors and have to buzz people in?
Something isn't right here and it's sounding like more than the shooter are at fault. Speculation of course, could just be horrible reporting
The kid knew the school. There is no conspiracy here. The shooting started inside the school and the shooter pulled the alarm and continued to shoot into the crowd and moved outside with the evacuating students. Early reports had the shooter outside with an accomplice setting the trap by pulling the alarm, this was not the case.
It absolutely was a security issue tho. The kid was known to the school and in his last year prior to expulsion he was not allowed to carry a backpack. Other students regularly talked about the shooter becoming a school shooter. This kid was a known security threat.
I think there is room here for legislation that allows a school to identify a potentially violent student and get some sort of a restraining order against the expelled student. The student (if over 18) could not obtain a firearm because of the restraining order, and would be required to surrender any owned until cleared of the order. This could extend to the household where the student is living. I can promise you that if my soon to be born child becomes violent or has tendency towards violence there will be zero chances for my child to come into contact with a firearm in my home. Responsibility is a large part of gun ownership. I may get flamed for this.