Dallas Police were targeted in a deadly ambush Thursday night when a sniper opened fire toward the end of a protest about recent police shootings in Minnesota and Louisiana.

The protest had been peaceful, some marchers even posing for friendly photos with Dallas-area officers, when multiple shots rang out. The attack killed five officers and injured 12. It ended when police detonated a bomb they delivered to the suspect with a robot.

It was a novel use of machinery normally reserved for doing just the opposite—dismantling explosives. But the suspect, identified as 25-year-old Micah X. Johnson, had been locked into place in a downtown Dallas parking garage and according to a report by NBC, negotiations to get him to surrender had “stalled.”

Dallas police chief David Brown said in a press conference that all other choices outside the robot “would have exposed our officers to great danger.”

This wasn’t the killer autonomous robot situation some experts have feared might become part of the 21st century battlefield, but it was, according to at least one expert in defense technology, the first deadly use of a robot by domestic police.

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(featured image courtesy of popularmechanics.com)