This fight is really boring to watch, so I recommend you don’t unless you’re actually playing the game and looking for help. I guess I’m posting this simply for thoroughness in documenting my journey through Bloodborne.
Anyway, this guy is a Major pain in the ass. Both his sword and gun hit for massive damage; just check out what his gun does to me at 0:34 in the video. Yeah, for real. He buffs himself, heals himself (one time), is fast and strong. The sword he uses, the Chikage, damages the wielder when used two-handed. The easiest way to beat this guy is to just stay alive and let his own sword do the heavy lifting.
After he heals himself and drops back down to around 30% health, he’ll no longer use the Chikage two-handed; it’s up to you to finish him off. I used poison knives. If you want to melee him, I’d recommend something with a lot of reach, like the Thread Cane or Hunter Axe (which can knock him down). Whatever approach you decide to take, the most important thing is avoiding that gun. Good luck my friends.