“I would use any tool necessary to save our officers’ lives, said Dallas Police Chief David Brown. (Stewart F. House/Getty Images)

It is called the ­Remotec Andros Mark V-A1, and the Dallas Police Department had the $151,000 device for eight years but had never used it before.

Then, in the early hours of Friday morning during a police standoff here, two police officers were confirmed dead and the gunman shouted at police that he planned to shoot other officers, as many as he could. So Police Chief David Brown did not think twice about sending in the robot to kill him.

“I knew that two of our officers had been killed, and these two were killed by this particular suspect. I did what I had to do to save our officers’ lives. I would use any tool necessary to save our officers’ lives,” Brown said during a news conference Monday at police headquarters.

The robot, nicknamed the Mark V, is manufactured by Northrop Grumman, based in Falls Church, Va. The device was specially configured for the department. However, police officials as well as a Northrop spokesman declined to comment on the robot’s specific configuration and use last week.

According to Northrop’s website, the device is driven by a human via remote control, weighs 790 pounds and has a top speed of 3.5 mph. It carries a camera with a 26x optical zoom and 12x digital zoom. When its arm is fully extended, it can lift a 60-pound weight. The “hand” at the end of the arm can apply a grip of about 50 pounds of force.

In this case, the device’s arm extension was carrying an approximately one-pound brick of the plastic C4 explosive, plus a detonating cord in a tactic that is used by the military in combat situations.

The shooter, Micah Johnson, a 25-year-old Army reservist, was hiding on the second floor inside a building of El Centro College, a community college downtown. By the time Johnson’s two-hour shooting rampage was over, five police officers were dead and nine were wounded, making it the deadliest attack on U.S. officers since the Sept. 11, 2001, terrorist attacks, according to the National Law Enforcement Officers Memorial Fund. Of the wounded officers, four were city police officers, three were officers with the Dallas Area Rapid Transit bus and rail system, and two were officers employed by the college.

Johnson, who was African American and had links to black nationalism, used an assault-style rifle to target white officers.

Policing experts are calling Brown’s decision the first time any police department in the country has ever used a robot in a lethal-force operation. Brown chose to attach an explosive device to the robot’s manipulator arm and then detonate it once the robot made it to where Johnson was hiding.

N.R. Jenzen-Jones, the director of a weapons research group called Armament Research Services, said robots have been used to examine explosive devices and manipulate small obstacles and have been used frequently to deliver different types of explosives to help breach doors or clear obstacles. Jenzen-Jones said, however, that he had never heard of a robot delivering a payload that was meant to kill a subject.

On Monday, Brown said that after discussions with negotiators, and after 15 to 20 minutes of mulling it over, he decided to send in the robot. His biggest concern was blowing up the school where Johnson was hiding. He warned the robot’s handlers of one thing: “Just don’t bring the building down,” Brown said. “But that was the extent of my guidance.”

Johnson was killed. And the robot, Brown said, suffered partial damage to the extension arm. “But it’s still functional,” Brown said.

College officials had not been allowed to assess the damage done to the building because it was under police control, Ann Hatch, a spokeswoman for the Dallas County Community College, which runs the building, told The Washington Post on Saturday. The campus remains closed.

The police officers had assembled to oversee a peaceful demonstration by activists who were marching against police brutality Thursday evening when the shooting began.

By the time police held a 12:30 a.m. news conference Friday, four officers were dead and police had been negotiating with Johnson for about 45 minutes. In that news conference, Brown said that Johnson was “not cooperating” with the negotiators and that he had told the officers that “the end was coming” and that he had plans to kill other officers.

“This person had delusions and was committed to killing officers,” Brown said Monday.

Brown also said Johnson told police that bombs were placed around the city, but at Monday’s news conference, Brown said there was no evidence of bombs.

Brown said that he asked his negotiators for their plans to end the talks, and that just after 1 a.m., the robot was sent into the building.

Brian Fung, Alice Crites and Thomas Gibbons-Neff in Washington contributed to this report.