The central test in the attorney general’s review is whether — in the heat of the moment — the police officer thought the person she or he shot was otherwise going to kill or hurt the officer or someone else. The review hangs in part on the standard of reasonableness — a legal test pervasive in the American justice system that is based on what investigators believe a reasonable person would do.
http://bangordailynews.com/2017/02/21/the-point/how-maine-police-shootings-are-investigated/
http://bangordailynews.com/2017/02/21/the-point/how-maine-police-shootings-are-investigated/