He was never depicted as having killed anyone on film, and there was never any suggestion that he actually did. Hector accepted his offer to be killed, but Gus chose to carry it out.
To be honest, Tyrus only seemed to taze Walt once over the entire season, and that was probably only because he was following orders.
Despite his lack of conversation, the man was presumably a good man outside of work. What if he was married and had children?