The outlook for the prolapsed mouse is not good at all. I recommend feeding him off or euthanizing him immediately to end his suffering.

Here is a link to a thread about some problems I was having with prolapses when I was trying to get my mouse colony started:
http://www.ball-pythons.net/forums/s...ad.php?t=79256

To give an update on that situation: I continued to have an occasional prolapsed mouse for a while. I'm not 100% certain, but I believe it was being caused by a bacterial infection. I'm also not sure if I ever really eliminated the bad bacteria, or just ended up with mice that are resistant to it. However, I haven't had a problem in many, many months, so it is something that can be overcome.

I can't even imagine why you saw he was bloody at the store, and decided to bring him home anyway. I hope you have kept him far, far away from the rest of your mice, rats, etc.