I bet there's been many people like him but at most it will be revenge fantasies against those they think are against them and it won't go much further. Knives and machetes are very personal and gruesome weapons to use but a gun is clean, precise and fast, plus far more mesmerising with the sound and visuals of the whole exercise.
What I'm saying is, revenge fantasies from the outcasts of society suddenly become far more achievable when you have such easy and legal means to obtaining lethal weaponry like automatic rifles. INA country where those aren't available these people probably wouldn't even consider it. But when those weapons are so easy to come by a fantasy becomes a very real achievable possibility that could tip them over the edge.
What I'm saying is, revenge fantasies from the outcasts of society suddenly become far more achievable when you have such easy and legal means to obtaining lethal weaponry like automatic rifles. INA country where those aren't available these people probably wouldn't even consider it. But when those weapons are so easy to come by a fantasy becomes a very real achievable possibility that could tip them over the edge.