Just watched the video. The kid sees the cop car approaching and walks toward it. The kid’s elbows appear bent so we can assume he’s holding the gun waist high though it’s too hard to see. The kid goes down immediately. The cops get out of the patrol car and have their guns trained on him. They walk around still keeping their guns aimed at him. It’s apparent they think the gun is real and he was threatening them.
Here’s an idea. Don’t walk toward cops with a toy gun without the orange tip. Don’t wave a toy gun at passersby. Don’t be stupid.