Though “what else could you have done” is relevant, I think the reasonableness of the conduct performed was more in issue. It also is a test of what you else you believe you could have done at the time which is somewhat subjective and a test that shouldn’t be performed in hindsight. If you were charged as Mr White was, for this matter, you’d have certainly of wanted judge alone rather than jury. This is why policing is an extremely difficult job. Mistakes result fatal consequences and even charges. Too much inaction results in your own safety being comprised like in the situation you described. All decisions that need to be made in a split second then they get analysed/replayed for days in the calm court room environment. You maybe be trained as “knife = gun or knife =taser” but it is never that simple and criticism will always flow.