Bantam Chick leg injury

[phoenix7]

I'm asking this question for my mother. She has 3 young bantams that she hatched for one of her classes(she's a science teacher), not sure of the exact age, but wings and legs are mostly feathered. One of the chicks seems to have injured itself somehow. She told me it was fine this morning, but when I got to her house this afternoon it was sitting in the corner of the cage, refusing to walk. I got it out and noticed that it has a blood filled abcsess of sorts on one of it's legs. I can't see a visible injury. Any ideas of what could have happened to it, and what I can do to help it? Thanks!

 

[LarryPQ]

PIctures would help.

 

[phoenix7]

Well, unfortunately an answer won't help him now. I went out to take a picture of him(I'd put him in a small tote to isolate him) and he found him dead. It's been less than 3 hours since I found him injured, and just 30 minutes since I last checked on him. He appears to have a belly full of blood. I guess he got injured internally pretty badly, although I'm not sure how.