On Thursday (July 7), a suspect involved in the fatal shooting of five police officers during a Black Lives Matter protest in Dallas was himself killed by police using a robot outfitted with a bomb.

In a press briefing on Friday, Dallas police chief David Brown said that a police negotiator spoke with the suspect, who was cornered in a parking garage, for several hours before talks broke down and both parties began exchanging gunfire. Brown said the police decided their best plan of action was to move in on the man using one of the department’s bomb robots, presumably the same disposal robots that many police departments use to defuse suspicious packages and bombs. Officers added an explosive to the robot’s extension, which they remotely detonated. Brown said other options “would have exposed our officers to grave danger.”

While Dallas police were not immediately available to provide additional details, it’s a rare occurrence that a police department would use a disposal robot to set off a bomb. The robots are designed to dismantle and defuse bombs, not wheel bombs into situations. Nor are these cheap machines; some cost upwards of $100,000.

It’s worth noting that these robots are not autonomous machines able to act on their own accord. They are remote-controlled vehicles that must be operated by a human. Here’s an example of one in action:

The US government has been using automated machines to take out targets for years—think drone strikes in the Middle East. Last year, North Dakota even became the first state to legalize police officers’ use of drones fitted with weapons such as tasers and pepper spray. Last night’s action likely won’t be the last time a remote-controlled device is used to take out a human in the US, but it raises interesting ethical questions about where bomb robots fit in police forces’ increasingly militarized approach to protecting the public.