I suspect most cops pay more attention to the motion than what's in the hand. If someone is "drawing" or "aiming", I doubt someone would have time to look down, determine what was in the hand, re-aquire the target, draw and fire if necessary before the other person could finish their action, no matter their level of training. If you think it's easy to do, try having someone at home do the same with a random object. I'm not defending cops, but I don't always think it's fair to call them stupid because they overreact in hindsight. It takes a quarter second to process movement, and if they are wrong about what it is, they could very easily be dead.
I'm not calling cops stupid (I'm about to finish rookie school...), I'm saying SOME are. In this instance, if it was a quick movement, then I guess I understand it more. If it was just a slow, deliberate movement of a banana he had in his hand, then no processing is needed. You can make that out pretty quickly. That's what I was getting at.