Before Dallas police used a robot equipped with a bomb to kill the heavily armed gunman who had shot 12 officers, killing five, more than 30 years had passed since law enforcement had used an exlosive on U.S. soil.

It's something Philadelphia will never forget, the bombing of the MOVE organization’s West Philly residence in 1985. Eleven inside were killed. The ensuing conflagration destroyed dozens of nearby row homes.

“When that bomb was dropped, killing 11 men, women and children, blowing limbs apart, you saw nowhere in the papers where they showed empathy for my sisters and brothers that were murdered,” said Pamela Africa, 69, a surviving member of MOVE who was not in the house at the time of the bombing. 

The home was bombed after a long standoff with police, who dropped two small explosives from a helicopter onto the house. That standoff followed a previous confrontation in Powelton Village seven years earlier in which a Philly police officer was killed.

To stop Micah Xavier Johnson, 25, a former U.S. Army reservist who allegedly used a semiautomatic AR-15 style riifle to kill five police officers and wound seven others guarding a protest of two recent killings of black men by police officers, Dallas police strapped a one-pound brick of C-4 to a bomb disposal robot, detonating it where they had cornered the shooter who refused to surrender.

Police Chief David Brown, who said they chose to use the robot after about two hours of negotiation with Johnson, told CNN that he personally asked his officers to “use their imaginations” to neutralize the threat.

"I approved it and would do it again if presented with the same circumstances," Brown said of the use of the robot., adding Johnson, who was believed to possibly have explosives, had taunted negotiators and asked how many cops he had shot.

“I began to feel that it was only at a split second he would charge us and take out many more before we would kill him… Without our actions, he would have, he would have hurt more officers,” Brown said. "I appreciate critics but they are not on the ground. And their lives are not at risk.”

Nonetheless, the use of a bomb delivered by a robot has led to some questioning of police use of force, adding to the debate already underway about police killings of black men. Protests have continued in New York City, Boston and Philadephia over the weekend, although all have remained peaceful.

“The use of a robot to not simply capture, but to kill a suspect, brings to mind all kinds of fears of automated assassination and potentially the dangers to ‘innocent bystanders’ in such engagements,” wrote American studies professor Javier Arbonna of UC Davis.

Others have said this use of force does not indicate new concerns about the “militarization” of American police, given the bomb was improvised by police.

“This was an ad hoc use,” wrote robotics expert Peter Singer in an opinion piece for CNN. “There is no doctrine that planned this out, no training manuals that police were following, nor development programs for this use.”

New York City police commissioner Bill Bratton said the use of the robot deserves public scrutiny on ABC’s "This Week."

"It is the first time that type of action has been initiated here in the United States and it deserves to be reviewed,” Bratton said.

U.S. police have previously used robots for tasks from surveillance to investigating potential bombs to delivering pizza to a suicidal man in California. But soldiers in Iraq and Afghanistan have reportedly used robots to deliver bombs.

To Pamela Africa, the use of the bomb amounted to police executing Johnson.

"It’s very, very clear that they did not want that man to live,” she said. “They did not want people to hear what he had to say, they did not want a trial … They sent that robot in, they could have sent it in with a chemical to knock him out. … It is factually obvious that they wanted to kill him.”

Additional reporting by Reuters