Sorry for late response He was a American Bulldog that was purchased as a house dog as a pup 6 weeks old, to replace my rottie. he was socialized loved other dogs but like people less and less as he got older if you approached him walking a dog you were OK let 3 minutes pass and you approach w/o dog he would flat out attack no growl no bark just go..I even thought maybe another trainer could see something I was missing and got 2 different people to try..he got both of them..the only non family member who was safe around him was a woman trainer who worked with him as a pup ( always at her place and always with dogs present) I had him at Univ of Penn for blood analysts and chemical makeup and I was told he had all 3 triggers for aggression ..even though he never showed dog agression..My son who was about 13-14 at the time had been with this pup everyday from the day 1 he went after him unprovoked with me present no warning( for 2nd time) just flat out attack..put him down that day I guess he was about 15-16 months at the end