Actually no, just because you kill someone doesn't mean you're going to jail. If someone is attacking you and you lash out in self-defense, you're very likely to not go to jail as everyone is expected to be able to defend themselves. It sounds very much like this was a defense mechanism to overwork. The fact that they didn't give him time off before approaching him was kind of crappy in the first place. It should never have come to what it came to.