I couldn't find Paul saying murders don't go to heaven. He said immoral. If morality allows for "state" change once, then his assertions on who fails to achieve the kingdom may apply to himself, as well as anyone else. But, the 'state' change morality argument lets down a huge number of denominations that believe once-saved-always-saved regardless of action, then Technically he wasn't a 'murder' if defined as killing people outside of legal authorization. Whether the instruction is not to 'kill' or not to 'murder' is a conversation for another day. For this reason, I try to find all answers outside of epistles, and understand them as reference points for other's viewpoint.