[CMay]

They don't necessarily know that's the only gun he had and the officers aren't Neo, seeing every camera angle at once. What you see from your outside perspective is not what they see. They have to act based on the information they have, which is why it's important you listen to law enforcement for your own safety. All the whistles make that harder, which might be part of the point.

[avcloudy]

Again: he was on the ground, with his eyes sprayed with mace, and he was, at least until seconds before he was shot, physically restrained. It doesn't matter if he could potentially have had another gun. They aren't Neo but there were six of them surrounding him, and the one who shot him only took eyes off to mace another protestor.