My GSD suddenly super aggressive towards another GSD
Dante, who's now 2 years old and perfectly trained, well socialized in all other aspects, met a friend's GSD this weekend while we were out hiking on the 4th of July weekend. Normally he's super super friendly with other dogs, extremely excited to meet them and with aggressive or fearful dogs, he'll just ignore them.
My friend's GSD is a little undersized, about 60 pounds probably. Just over a year, and SUPER hyper and energetic. I don't know why it's just with this one, but whenever Dante would go near Mikhail (the other GSD) he would bare his fangs, growl and suddenly attack him (paws on him, flip him over, snarling, and show dominance). The other dog would screech and belly up and cower (ears flattened, avoid eye contact) until dante left him. And then when he would try to slink away, Dante would run at him and flip him over again, snarling.
Why would this happen? It's just with this one, Dante has never otherwise shown aggression. There weren't any unfixed females around or otherwise.
Anything else you can think of that might trigger this? Dante is not food aggressive, (and there was no food or treats around). Mikhail was not aggressive towards me or anyone else.
One of the times Dante flipped him over, Mikhail was struggling and Dante bit down on his leg and his tooth gashed a pretty deep cut into his upper thigh. Needless to say, this is worrying me a lot and I'm not sure what could possibly make him act this way.