By better background checks, what some mean is a check of things like internet posting which may give a different viewpoint of the individual.
The background check for a security clearance involves being interviewed and interviewing one’s neighbors and friends. This would be telling if applied to the Parkland shooter. So I would permit an escalation of the review if the individual was initially found to be in a questionable area. BTW, I am not sure what would be the tip off, but being expelled from school would be one thing I would wonder about. There are other markers and I would appreciate that the individual should be able to appeal.
“...what some mean is a check of things like internet posting ...”
Like we do here on FR?
By the way, what’s your real name, address, phone number, and
Social Security number? I haven’t read all your posts but I have no doubt someone somewhere wants to contact you about them.