The Dallas Police Department’s use of an explosives-armed robot against the shooter killing its officers Thursday night was a remarkable and perhaps inevitable weaponization of a familiar and popular technology.

Aided by federal grants and Defense Department assistance, hundreds of civilian agencies have equipped themselves with robots. But using an explosive ordnance disposal robot for a lethal purpose raises distinctive legal and policy questions.

“These EOD robots have been used for many things,” Dan Gettinger, co-director of Bard College’s Center for the Study of the Drone, said in an interview Friday, “but this was pretty unusual.”

Elizabeth E. Joh, a professor at the University of California Davis School of Law who specializes in surveillance and technology issues, said she thought the Dallas incident marked, in fact, the first time American police had intentionally used a lethal robot.

“We already see surveillance robots,” Joh said. “But a robot that is capable of harming or killing people is a game changer.”

It raises larger questions, Joh said, such as, when can the police justify the use of a lethal robot? Should we permit lethally armed robots to conduct ordinary police patrols? Should citizens be permitted to own lethally armed robots?

Dallas officials revealed Friday that officers had attached a C4 explosive charge to the robot’s extension arm, sent it toward the shooter — now identified as 25-year-old Micah Xavier Johnson of Mesquite, Texas — and remotely detonated it, sacrificing the robot to the cause.

“This was a man we gave plenty of options to,” Dallas Mayor Mike Rawlings said.

“This must have been a pretty extreme situation, given how much those robots cost,” Sean Bielat, chief executive officer of robot manufacturer Endeavor Robotics, said in an interview Friday.

Bielat estimated the robot used in Dallas might have cost about $100,000, although many details were not yet available Friday.

Robots themselves take many forms, from 5-pound gizmos that can literally be thrown around for reconnaissance purposes to 20-pound and 65-pound devices, as well as a 500-pound behemoth that Bielat’s company makes for use with car bombs.

The military is the biggest market for the bomb-disposal robots, but the Pentagon has helped spread the wealth to civilian law enforcement and emergency agencies.

From 2003 to June 2016, government records show, the Defense Department transferred 682 bomb disposal robots to 241 agencies in 41 states. California received the most, at 160, followed by Texas, with 122.

Recipients ranged from modest-sized agencies, such as the Manteca Police Department in California’s San Joaquin Valley, to federal law enforcement offices, like the Bureau of Alcohol, Tobacco, Firearms and Explosives office in Wichita, Kansas, to the large Texas Department of Public Safety.

“There’s a very strong interest among law enforcement agencies in getting robots out there,” Bielat said.

The Dallas Police Department’s Explosives Ordinance Unit announced in May that it had acquired “a new vehicle, new robots, new bomb suits and new tools,” although police did not specify Friday whether it was one of the robots that was used Thursday night.

The Tucson Police Department’s SWAT team, for instance, notes that “tactical robot operators” are among the team’s specialists.

The most common police use, until now, was typified in a previous Dallas incident in June 2015.

After James Boulware fired on police headquarters and exchanged gunfire with officers, police used an ordnance-disposal robot to confirm Boulware was dead and then check his armored van for explosives.

Gettinger, of Bard’s Center for the Study of the Drone, noted that the U.S. military has experimented with equipping robots with grenade launchers and semi-automatic weapons, among other lethal devices; so far, Gettinger said, without marked success.