Like all things involving the Church, Porter probably did none of the killings LDS scholars attribute to him, and all of the killings they deny ever happening.
Actually, from what I understand, all his known shootings were from the period of time when he was a Deputy US Marshal for the Salt Lake division of that service. That isn't to say he didn't do some killings of church enemies on the side, it's just that is what is officially known. Maybe the church has records on the unofficial stuff buried in the special vaults?