I doubt this was the first time.

The drone, which can be directed to detonate on impact, was operating in a “highly effective” autonomous mode that required no human controller, the New York Post said.

Some weird mix of “follow me” and “failsafe” modes. Oh, and the put a claymore on the drone.

Source: A rogue killer drone ‘hunted down’ a human target without being instructed to, UN report says