There isn’t any information included with the video to give the details of where this took place.  But it looks like a high school gym somewhere at the end of a blowout.

As you can see in the video, a referee attempts to block a halfcourt three pointer from behind.  He wasn’t successful, the kid nailed the shot and then gave ref a quick stare before celebrating.

Given the fact that the referee tried to block the shot and it still went in, they should have given him four points making it.