You're about to see a working NERF sentry gun. A proper sentry gun, like one you'd see in a video game or movie, which can automatically track you then start shooting until you die (of amazement).
It was built by Instructables user BrittLiv, and comprises a NERF Vulcan gun, a stand, a motor and a laptop. Using recognition software, the laptop's camera can track someone walking in front of it, the gun moving to follow the person's movements.
While it can be fired manually, as you'll see in the video below, it can also be programmed to shoot automatically at targets (and even programmed to not fire at certain people).
In summary, this is an autonomous motion-detecting, belt-fed NERF machine gun.