Who really killed Tetsu's parents?

I mean ichimura tetsu from peacemaker. I got a little confused bec. at first I really thought that it was Yoshida but in the end when Tetsu asked him why did he kill his parents he just answered "what are you talking about?" I don't know if he only did that to confuse tetsu at the moment or was it really not him? When I read the manga I suddenly had the thought that it might be hijikata. I haven't finished the manga yet.