Gun control won't make anything better, if not worse. People like this use guns because they are easy to get, gun control would take that away. There is a stuff-ton of legal chemicals and items you can buy to assemble a bomb, lets say a pipe bomb for instance. One or maybe even a few of those could do a lot more damage than a gun.
Gun control is only going to encourage people like this to seek out even more dangerous ways to cause harm.