It wasn't just a "cry for help," that's for sure.
Actually, taking your life in a gruesome way is considered a classic hostile act. It’s a way of punishing your survivors, as well as society (in the form of people who happen to be present), and saying “see what you made me do?”
I don’t know what triggered it in this case, but he was probably one of those people who had fantasized for a long time about doing something ghastly like this as a sort of parting gesture of anger and self-pity.