Oh and I meant to add, I don't know what people made of this, but after I interrupted Cain with a shout and he stopped instantly, I put him straight on his bed and told him to stay, which he did. The weird thing was that within 30 seconds of being put on his bed, he closed his eyes and rested his head on the floor. It was strange as I expected him to keep an eye on Tim if he was that freaked out by him Why do you think he was willing to close his eyes? Is it a sign that he wasn't that worried? Or is it some sort of shutting down coping mechanism? He seemed normal enough.

Also when Tim had to leave, to diffuse his movement and to finish on a positive I gave Tim treats to scatter on the floor. However Cain came over and wanted to take them out of Tim's hand before Tim had a chance to drop them. I got Tim to throw a huge handful on the floor to distract Cain. By the time Cain turned around, Tim had gone. But Cain seemed perfectly happy to attempt to approach him again for treats

Thinking back to the incident, Tim said he wasn't touching Cain at the time, but Cain was standing in a small area between two armchairs so maybe he felt trapped?

Sorry for the meltdown, I just find his aggression towards people so much harder to deal with than his aggression towards dogs, it really upsets me. It scares me how he doesn't give any clear warnings, how he's unpredictable, how despite all my efforts I still live in fear that one day, somehow he might bite someone, get taken away and put to sleep. I think that's why it affects me so much and makes me feel so low. It helps to be reminded that there are people out there who are going through the same thing and feeling the same way too.

Cain's breeding is to guard against all comers. He will bite an intruder if he is not told otherwise, that is just in his genes imo. My BK is exactly the same but you know that is a possibility with breeds like that. If I was you I would accept that and then work from there. So think of it as - Cain is starting to accept tim! That is one more person.