The more time that goes on the worse it gets.
Just like Parkland eh?
When are the American people going to stop with the "hero worship" and burn all of those "blue line" flags?
The shooter was arrested four years ago for threatening to do exactly what he did, when he did it. Obviously he was not prosecuted and convicted because if he had been he couldn't have walked into wherever and bought guns. Therefore he didn't have a felony record despite apparently presenting sufficient evidence of a felony.
There's a record of this, of course, which the media and Texas Government will do their level best to bury -- of course they have thus far, and won't talk about it.
Then there are many reported threats by others he knew to kill and rape women both online and in "real life"; that seems to not endear people to him who he wanted to date (go figure) but that didn't get him any attention either, including from the rubber room crowd who can, assuming the claims were real (and due process followed) issue a nice involuntary referral to a mental institution. Of course you have to actually give a crap as a government employee for any of that to happen. It didn't.
Folks, there are so many incidents of refusing to prosecute obvious felonies that the law has become a bad joke.
It seems that in most of the recent nasty cases of this sort there was not just the opportunity to interdict the attack it was not on a speculative basis either; the person who did it not only gave "fair warning" of their intent they committed prior felony offenses months or even years in advance in giving said warning that were sufficient to arrest the perpetrator and the police, prosecutors offices and/or judges deliberately refused to do so.
And while there's question as to whether this is all accurate there's plenty of record that his being perfectly ok with being called "Yubo School Shooter" on an online platform wasn't a cause for concern on his part nor an investigation by anyone else, specifically (once again) said rubber room folks.
Stop blaming "guns" folks. Guns are tools and damned useful ones if some nutjob is popping kids.
If someone tells you four years in advance they intend to take a chainsaw into a school and play Anakin Skywalker in the Jedi temple getting rid of guns will not stop them from acquiring a chainsaw. Or a Suburban. Or any one of a bunch of other nasty things, some as simple as a few cups of gasoline, a couple beer bottles, an old t-shirt and a BIC.
If said prior warning rises to the level of an arrestable felony offense or is grounds for involuntary commitment to a mental institution yet the offender was not prosecuted or so-referred then save me all the whining four years later when said person does exactly what he said he was going to do, when he said he was going to do it and direct your ire and retribution at the so-called "law enforcement" structure in that part of the country which intentionally, willfully and maliciously did not do its job.
It's pretty damn hard to shoot up anything if you're either in prison or confined to a rubber room.
PS: When you get done directing your anger over this incident at the appropriate people, which appear to be the government of the state and county involved you might consider doing the same with the federal and state governments that have willfully, maliciously and intentionally ignored felony violations of 15 USC Chapter 1 for the last, oh, three decades or more. You will find most of what ails our economy, medical system and more right there.