Cat Started Bleeding

I noticed today that my cat had a mat of fur on her back. A few hours later, I noticed again while she was sitting on my lap. Thinking nothing of it, I tried to sort it out and it came off easily in my hand. Not a lot of fur came off, but a lot of blood started coming from her. I immediately applied pressure and the bleeding stopped after just a minute or two, but the blood smelled really bad, like stool. Has this happened to anyone else's cat? I have no idea what to think. She seems fine, but I'm still worried.

Is it possible that the mat itself was comprised of dried stool, and that's what the smell was?  I realize that doesn't explain why she bled, but that might explain the smell.  Otherwise, I have never heard of blood that smelled like stool, and never heard of excessive bleeding from removing a mat unless you were using scissors and cut her accidentally.  Could that have happened?

When in doubt, call your Vet. 

Sounds like an abscess. She should see a vet.