We will never know why he killed, or how he got the guns. Yes I know from his mother. Did she have a safe? Did he say hey show me how to clean then in order to get her to unlock them? We dont know.
the definition of crazy is, doing the same thing over and over again, and expecting a different result. BAN BAN BAN, we ban killing, we ban guns in schools, in malls, we ban all these things and expect a change. But bans dont stop human nature to kill.