Another School Shooting

Yesterday, another school shooting took place. Six people killed including the shooter another ten wounded.
Again the cry sounds, they (the schools) got to do something about it. I agree but I'll be dammed if I know what is to be done.
They can get metal detectors but a smart person can still slip a gun by them.
How do we protect the students against a person with a sick mind? Both the VT and the shootings yesterday were done by a person who either was on meds. and stopped taking them or by someone who has had psych. problems. The school staff are not trained enough to spot these people let alone treat them. And of course not all people with psych issues commit such terrible acts.
We cannot remove these people from school. The lawyers would really enjoy it if someone tried. So just what do we do?
We could hire more police/guards to patrol the halls at all times but can you guess the cost of this ? And these added costs would be passed on to those enrolled and there are too many that can't afford this level of schooling as it is.
Saddly, there is no real easy answer to this question.
Could tougher gun control help ? It might but anyone who wants a gun bad enough can get one on the street for the right price.
Schools should be a safe place where one learns about a great many things. Where everlasting friendships are formed, careers are choosen. One should not be worried about how to get through a school shooting.
Like I said, I'm losted for a answer, I don't know of one. Do you?
Rest In Peace those who died. nuff said