For this bossfight I used the
Z.A.R. (click for link) combo weapon. Only needed one. Way easier and faster with it then any melee weapon.
Also don't forget to do the
dodge-roll (click
+ any direction) when he/she charges at you.
If you have the book
Fortune Figther (click for link), equip it and use it in combination with the Z.A.R. , it increases the damage inflicted with firearms.
Here's a video of "
Gameocalypse" (credits and thanks to him) beating that psychopath: