Oh my God! As everyone else said...take Kingston to the Vet ASAP!
That lady is an idiot! Why are there so many idiots with Pits? They make me want to slap the crap out of them. She should have pulled her dog back. Better yet, she should be training her dog to walk by other dogs properly. This is so very sad and I pray that Kingston is okay.
Everyone...bring mace with you on your walks, and from now on if a large dog comes towards you and your baby, spray it and start screaming! Let them ask questions later. That will teach these idiots to BACK OFF!