How do you safely and quickly dispatch a wounded deer?

After reading the other post today about the [first time hunting] (http://www.reddit.com/r/Hunting/comments/144sym/took_my_first_life_today/), I realized I could be in a situation where I walk up on a not so clean deer kill and I have no idea what to do. I guess it's the same as when you are bow hunting, but in that case I think normally you would just wait it out.

Wouldn't it be dangerous to take a close up rifle shot? I don't know if I'd have the stomach to pull out my knife.