This is basic stuff - when people are attacked, they become defensive.
He wasn't being "attacked"... he was being asked to comply with police requests. Your definition of the man being attacked is what was fantastical.
Pretty much everyone, even a foreigner who was here on his first day, can recognize a police officer.
Most mentally ill that aren't institutionalized, can still absolutely recognize a cop from a normal person.
I still believe it was mental illness that caused him to refuse to comply and talk with the police, but it doesn't mean i think the man didn't know they were cops.
I've dealt with homeless a lot having lived in bad parts of town in the past, and mentally ill or not they knew who the cops were..
And sadly, the people around the homeless know who they are, and know which ones are worse off than others and generally look out for them.
I used to buy coffee for a homeless man every morning, my husband bought him lunch every day and a friend of ours made sure he had clean clothes to put on .. His mental health issues were so severe he couldn't care for himself, but no state entity would care for him either.
Had I seen cops speaking to him I would have spoken with the police on scene to explain the mans mental health condition to him and give pointers on how to deal with him best. (And so would every business owner and person in that neighborhood have done the same, we all knew him well).
Leaves me wondering why this particular homeless man (the one killed in this encounter) had no one in the area looking out for him, yet everyone happy to stand around filming the encounter.
People in general need to do more for others, and stop all this nonsense based in their own hatred of police.