There has been a movement titled, "Breaking the school to prison pipeline," active in schools for over a decade now. The focus is on NOT reporting crimes committed on school grounds to law enforcement. School systems like this, because they don't have to report violent events in schools. Law enforcement is cooperating with this. Students who are obvious dangers and criminals are not being referred to LE or prosecuted, resulting in 18 year-olds (whom everybody knows is a threat) having a clean criminal record, and being able to buy a rifle.
I know this is not the case in this particular school shooting, but not reporting threatening students is par for the course today. Additionally, that is EXACTLY what happened to lead to the Stoneman Douglas school shooting.
I'm not just spreading rumors. I've been in the staff development sessions. It's active in your schools. The administration and LE talk tough about keeping your kids safe, but they're happy to sacrifice them for political ends.