Re: We're all second guessing...
If there's open windows,
Car park - all open. So the only way to knock him out without a fight was to simply drive one of those armoured personnel carriers police has bought with Bush and Obama's grants up to him at point blank range and point the 50 cal at his head and ask him nicely to surrender.
Not particularly difficult, kit was available (Dallas police is a recipient and has them), they deliberately decided to execute him instead of putting him in a situation where he had no choice but to surrender.