This may be radical. I think the shooting was caused by his gambling addiction. He was a highstakes gambler that always figured his odds and did everything to better them. To him, this was the ultimate gamble, shoot everyone up and escape( the sheriff believes he intended to escape). He did everything to better his odds, but didn't calculate that a security guard would arrive so quickly, trapping him inside. He lost the bet, so killed himself( as well as a lot of others). Instead of worrying about the tools, we should study the addiction and how to deal with it.
Mike