You have likely seen headlines similar to the above, referring to the aftermath of the targeted shooting of a dozen Dallas police offices following a peaceful demonstration against two earlier civilian deaths by police officers in other US cities. Five of the dozen Dallas officers have died so far.
The suspect was cornered, well-armed and negotiations had broken down. The Dallas police sent in a bomb-disposal robot, which can typically carry explosive devices in order to safely detonate bombs. This time, they used it to detonate the suspect.
Now, it should be made clear that "robot" in this context does not mean an autonomous device; these are remote-controlled driveable "drones" if you will, and someone is "at the other end" controlling the robot.
The US has already used airborne drones to kill Taliban and others overseas (and as a result killed civilians in the vicinity). We have not, to my knowledge, used aerial drones for such a purpose on US soil, and this is certainly the first time it has been reported that a civilian has been killed by a police robot or drone.