Who the *beep* shot Rhino?

I was wondering the same thing. The only thing I can think of is that Shavoo had a gun in his hand underneath him but they didn't do a good job of showing this.

Here's the answer:

Shavoo shot Rhino. He had the gun in his right hand but it was under his body as he was crawling, so Rhino didn't see that he had the gun. Rhino thought he was unarmed, so when he was reaching down to cut his throat, Shavoo just moved his hand up and shot him. You see the bullets exiting through his body from the front through his back and you are supposed to be able to tell from the direction of where the holes appear that Shavoo is the one who shot him.

I thought it was quite obvious, but I saw this on DVD didnt know if the theatrical version was cut any differently?

The director explains the scene on the DVD.