My rottie mugged another dog today and it is not in his nature to do that. I'll tell you how it all happened and I ask for advice on what to do and reasons as to why this might have happened.
Brief history on Boof: 6 approx years old, got from pound as a 12 month old, very social and friendly, lives with a kelpie x who is 11 months old. He is desexed and has good basic training (sit, stay, lets me take his food while he eats, etc)
Recently he has had an extra dog in with him and Roxy. she is a 7 month old staffy and all 3 dogs have been playing fine and sleeping together. they all eat together and the only time he growls is if the staffy trys to steal his food but this has now stopped as she has been getting fed far away from him so she doesnt bother him.
When he plays with roxy he is good and will dominate her if she gets too full on but its not nasty and he never bites. its more of a quick sharp grawl and a paw pushing her down in a "no thats enough" fashion. He does this with the other puppy too and she just rolls over and submits straight away.
Today all dogs were walked/run and a swim in the pond a couple hours before the incident. all 3 were back in the pen and we were out working on the motorbikes. the dogs had been in the pen about 2 hours (give or take) when all of a sudden the staffy screamed and u could hear boof mobbing her. by mobbing i mean pinned on the ground mouth over her throat (no teeth) and grawling with aggression that I had never seen before. I called him off but he wouldnt stop, luckly i was able to open the gate just enough and the staffy ran out and he was left in with roxy.
I checked the staffy from head to tail and no marks but lost of drool on her body and throat and was a little shaky. Both dogs were back to themself like nothing had happened after 5 mins. They are now apart and will stay that way for the night.
so thats what happened. now i need ideas on why it happened and what I can do to make sure he doesnt do it again. I dont know what set him off and it worries me. He is my best friend and I dont want him to have to be put down but if this is more than a one off and means he wont be safe anymore around other dogs or kids then I would have to