Take down all the priests around the place and keep running..once thier all dead walk instead, he can't here you as well then. The trick is to bait him to swipe like crazy while retreating far enough to get a good shot on that parasite on his back while being out of his range. If you wanna make him go down faster you can run in close after his attacks over. Something strong like shotgun/striker/broken butterfly is a good weapon to use.
Now I know that sounds stupidly hard, but yeah, it can be pretty tricky...took me a few goes first time too!
Anyway, as long as the dudes surrounding the cage are dead, your free to take your time a bit more and think it out.