As I said, I can shoot MOH (Minute of Hajji: not a perfect grouping but accurate enough for consistent hits on a man sized target) all day long at 100m with my carry gun. It takes effort, but its by no means impossible or even very difficult to do.
And again, its 65 yards from door to door. Distance to the gunman was probably less than that, and even door to door is by no means an incredible feat.
Sure, if you miss and by chance hit one of the people in there, you could be faced with charges. Simple solution: don't miss. Really, its that simple. Training will get you there.
Were I in that situation, I'd probably close distance. Closer = easier to get a grasp on the details of the situation and of course an easier shot at the target, not to mention the cover provided by obstacles in the parking lot.
Had the BBQ guy done so, and stopped the gunman while he had the chance, lives could have been saved.
As trlcavscout said, there are situations where its best to get the hell out of dodge or be a good witness. And "active shooter" scenario where large body counts are the goal is not one of those situations IMO.