Brown didn't know that at the time. He'd have every reason to believe he was about to be arrested for theft and assault of the store clerk.
and that could be true as to what is going on in his head.
I would agree with you, EXCEPT, that wouldn't explain why Big Mike and friends thought it a good idea to block a police car coming down the street.
If that were truly the case, wouldn't they have been 'chillin' and tried NOT TO BE NOTICED ?