Hi, today Yogi started to become very aggressive on the leash. Up until now he has just come up to strangers on walks and sniffed them but today he growled at 3 people and actually bit 2 of them on the jacket with the front of his mouth. I have just signed him up for obedience classes at the MSPCA but I am currently awaiting on their response to whether or not he will be accepted or if the date i chose is OK. What should i do about walking him until then? I bought a prong collar just in case something like this happened but i haven't used it. Should i start using it until we get to the class or just take him out to use the bathroom only until the classes start?