I had a similar situation several years ago with two former dogs that have since gone to the RB. Whitney, my standard poodle, had been playing in the next room with Ashley, my miniature poodle. All of a sudden I heard ungodly yelping. I ran in to see Ashley hanging from Whitney's collar by her jaw. It only took a second to free her, but I shook all over for about a half hour after it was over.

I never put collars on them again (except for walks or grooming) and Bella and Ripley don't wear them except for walks/grooming either. I am soooo glad you were there when that happened and that both dogs are OK.