I would go back on schedule. No doubt with a view to assessing the situation as I was there. Perhaps he'll have moved on and there's no further threat. Perhaps they'll have improved his medication by then or started him on some. Perhaps his 'mate' will be there next time and he'll not feel threatened.
Don't bin it Steve, cos if u replace it with two one of them might be his mate and he's a right nutter. And don't go down Walter Mitty's suggested route cos the guy isn't a dog thats shat on the lawn.
You'll be alright steve, let's face QPRs ground is full of 'loose cannons' and you go there.
I suppose it can depend on the life experiences that you've had. I once had a very good friend who killed his mother when he had a mental illness - sliced her open "to let the devil out". Although it was clear he had some sort of problem, paranoid schizophrenia wasn't diagnosed till after the act. Although I didn't witness the act, I suppose it's left an indelible scar on my memory. Now I do realise that a person with psychiatric illness is more likely to harm themself than a third party but, after that, I would be unwilling to take the risk. If you have not encountered something like this in your own life, I do understand why it wouldn't raise a red flag with you.
The last I knew of him he was in Broadmoor. The act took place about 35 years ago. I know he was still in there 10 years later. I stopped visiting around that time because I felt a need to move on.
The odds are that you are right and that there will be no problem. The odds were also that my once friend wouldn't kill his mother.