It is a justification. It’s always, “He could’ve had a gun.” Well, he didn’t have a gun, and if police have the right to shoot people to death, then they better be trained enough to determine whether or not someone is actually a threat. Too often, they do that incompetently. Also, if we’re going to live in a country where everyone has a God-given right to bear arms, then “he might’ve had a gun” shouldn’t be an excuse to kill somebody.
I certainly agree that an officer can’t shoot someone just because they might have a gun. But police are legally justified in killing if they act out of a reasonable fear that there is an imminent threat to life or serious bodily harm. Sometimes there might not be a gun but the fear is nonetheless reasonable. Waiting to determine if there “is actually a threat” means it can be too late for the police officer. In this case, given the distance, I don’t know how reasonable the fear was if the guy only maybe seemed to reach toward his waist. The police would likely say the call they received played into their “reasonable fear.”
To see how difficult these cases are, you can look up the shooting of Daniel Shaver. The officer was prosecuted for the killing and found not guilty, under a disturbing set of facts, there is also video.
I think Warbler is saying the officers might have been justified. And maybe. I’m very skeptical given what we do know. We need a lot more information.