Is that the shooter used his father's guns. The father was presumably not a victim of mental-health issues. He probably missed the signs that his kid was about to go off the rails. Texas is a very pro-gun state, so good luck getting its citizens to prevent their kids from taking a pistol or shotgun out for a ride. As the kid was only 17, he couldn't legally buy a handgun. But how can you absolutely prevent a messed-up kid from raiding the gun save?
Please don't say, "Ban all guns," or something akin to that. It may have worked in the UK and parts of the Commonwealth, but it isn't going to happen in the U.S.
Maybe if the perps got less spectacular coverage, the wannabes would be less inclined to try to outdo them. The recent spike in shootings looks an awful lot like a few losers trying to get their names in the news.