Did you fail to notice the flawed methodology of the study. A person is shown a single photograph for a few seconds, no audio, no interaction, just a single frozen image and they have to make a judgement call. Nothing EVER goes down like this in the real world. There is always motion and there is always action, and THAT is how you judge intent. The participants did not even seem to be actual gun owners, who might take time to familiarize themselves with the deadly force laws in their state, but rather were apparently college age people without any mentioned firearms background. Flawed.
It's beside the point that the whole premise of the study seemed to be the police saying, "Hey, yeah, we sometimes shoot innocent people, but our job is HARD, man! Look, you can't even do it right either, so cut us a break."