BIG mistake about the killer
I just finished watching the movie and when the boss is attacked and loses the eye, you can't see the killer face but you can see he is wearing Craig's black leather jacket.
The fact that they didn't show the face of the killer led me to think they were going for some kind of twist at the end... so it didn't made sense to me when they showed the killer wearing the jacket through the bottle and then we can clearly see the jacket sleeve with the zipper strangling the owner while Bill (the killer) was wearing a blue shirt with no sleeves.
You can see what I am talking about in these screens:
http://imageshack.us/a/img822/6303/0djl.jpg
http://imageshack.us/a/img35/6550/me7r.jpg
http://imageshack.us/a/img853/2235/e8w4.jpg
So they SHOW YOU Craig killing the owner and then in the end the killer is Bill, unless we are supposed to believe that Bill put on the same leather jacket, killed his partner and then toss it somewhere.