Here's something to think about ...

The reason deranged people like this kill with semiautomatic rifles is because that's the weapon of choice in our culture when it comes to violence in movies and games. Imagine if it was an SUV. What if most of the games were based on running people down in vehicles? Then wouldn't the mass murders be done with vehicles?

It's not so much that violent murderous films and games make people imitate the violence, it's that when they do, they use that weapon - military style rifles. In the cowboy days, it was pistols - it was always gunfights with pistols. Now the media show big sexy military rifles, all ugly and black and scary, mowing people down.

The deranged freak job says "yeah, that's what I need", and he buys a measly AR-15 to pretend he's that bad-ass guy. Coulda done the same damage with a couple of boring pistols, or a big SUV, or fentanyl in the food. But that's not how it's done in games and movies.

... might have something to do with the problem ...