I’m really sorry to hear about your dog, and your pet sitter. I hope they both recover.
I live near there and I have seen a short, stocky, pit bull roaming. It has a pink collar. I believe that the dog lives on Kennedy, btwn 14th and 13th. Each time I see the dog, it seems to come out of a yard on Kennedy (I was farther down the street and could not see which house, or tell if it was just walking through the yard) and is always headed to the corner of Colorado/Kennedy/14th. I couldn’t determine where it went from there, but that’s very close to where your pet sitter reported the incident. The dog basically ignored me, but I did not have my dog with me either. I had called animal control on the second time I saw it, but I’m not sure what follow-up, if any there was.