Is a cruise missile a robot?
Is a drone a robot?
The Key Words are; Fully automated and autonomous.
A cruise missile is a robot but it is not autonomous. It follows a programed path to its target. It does not make decisions. So, it is not autonomous.
A drone is not a robot. It is a remotely piloted vehicle. It is not autonomous, it has a pilot back at its control center.
the drone is guided (not the same as piloted), but is the targeting automated?
An armed drone circling and running an area-denial program meets your stated criteria - at least until it gets a recall message or runs out of fuel.
Swarms of such drones have been tested in simulations (and probably in live field actions too)
Stationary robot sentry guns also been tested in Korea, which can automatically track human or vehicle shapes and fire on them after they get a "weapons free" message.
Mobile vehicles with similar capabilities were tested in Saudi Arabia - about 20 years ago. They broke down a lot in the trials and were eventually scrapped. But a lot of technology improvements have become available since then.
Urgent pleas to lock the barn door after the horse has already left are somewhat ineffective.