I'm not normally of the school of thought that quadrotors should be terminated with a shotgun, but then again I've never seen a DIY drone just casually flying around with a handgun. Until now.
The YouTube video doesn't give much to go on, other than that this is a) a homemade drone, and b) very much firing what looks like a working handgun. It even deals with the recoil just fine, meaning it can probably track down and kill multiple humans at once. I'm not saying you should start preparing for the Skynet invasion by stockpiling 12-gauge bird shot, but it's probably not a terrible idea.