Get a vet at the earliest. I guess you must have already attended to it. Always remember that bright red blood in stool is probably from dog's rectum or colon. Normaly a vet would suggest you to go for hematochezia. Not sure if you can avail guidance from animal control specialists like hawkeye (
Animal Control Toronto | Wildlife Relocation Service | Hawkeye) . Give a try since they rehabilitate injured animals they might help you in this matter too. I pray for fast recovery of your dog. Check out for more details at pethelpful.com