Speaking from experience. I adopted a pitbull about 10 years ago. Spent countless hours training it, sent it to a daycare to make sure it was socialized.

Strike 1 was when he got kicked out of the daycare for fighting. Strike 2 was when out of nowhere he bit my friends dog. Strike 3 was when he turned on my border collie and nearly killed her. She was the dog he grew up with and spent every single day with. I had to beat him with a grill spatula to get him to let go, and I was bitten in the process.

My observation with the breed was that they have an instinct built into them and when it triggers they become possessed and they lose all control. Humans don’t usually trigger it, but other pets tend to.