NEW YORK >> Police radios crackled to life: someone was shooting inside Bronx-Lebanon Hospital Center. The gunman — an “active shooter,” in police parlance — was spraying bullets from a semi-automatic rifle at doctors and others, moving toward the roof and, according to fractured reports, setting fires.

It was a deadly horror unfolding in a building created to save lives.

But to New York City’s counterterrorism officials, the frantic second-by-second dispatches June 30 were something else: A real test of new anti-terrorism plans.

In its earliest moments, the hospital shooting sounded like the kind of low-tech assault called for in the pages of the propaganda magazine Rumiyah, which the Islamic State publishes for potential terrorists. It mirrored a siege on June 1 of the largest hotel-casino in the Philippines by an armed man carrying gasoline canisters. And it was similar to a recent training exercise: a scenario that New York police and fire officials had invented for a three-day tabletop drill just weeks earlier.

In the end, the onslaught at Bronx-Lebanon was the work of one man, a disgruntled former employee, who died in the assault along with one of his victims. Still, it provided a crucial trial run for the new anti-terrorism tactics.

Those include a system in which armed officers escort paramedics to the periphery of mass shootings to save bleeding victims; the fast response of elite officers armed with long guns (180 police vehicles arrived at the hospital in minutes); and a new doctrine in which the first officer on the scene goes in fighting, no matter what. All these tactics were put to work that harrowing day.

“We constantly need to strive to adapt our strategies, our tactics, to face the world that we are living in and that is exactly what we are doing here,” said James E. Leonard, the Fire Department’s chief of department. An after-action review is ongoing, he said, to see “what went well; what can we do better.”

On display that afternoon was the so-called Rescue Task Force, groups made up of paramedics and officers trained to face gunfire to care for victims so seriously wounded they might bleed to death before help arrives.

The protocol calls for officers to go in and render an area — a hallway, lobby, staircase or floor — safe or “warm,” before forming “a force protection team” around a cadre of medical responders to “take them inside to start to do triage and start to remove patients,” said John J. Miller, the Police Department’s deputy commissioner of Intelligence and Counterterrorism.

The paramedics wear tan military-grade bullet-resistant vests and helmets, said Leonard, who said 10 teams are “on duty at all times” around New York.

The concept contrasts with previous tactics of having counterterrorism forces clear a scene before allowing medical personnel inside. And it solves a challenge law enforcement has confronted since as far back as the Columbine school shooting, in 1999, and as recently as the June 2016 attack at the Pulse Nightclub in Orlando, Florida: How to fight an armed assailant in a sprawling venue, such as a mall, theater or office building, while also tending to the injured.

“There are cases that would benefit from a minute’s difference of high-quality medical response, as opposed to people laying on the ground while you cordon off the area,” said Juan C. Zarate, a deputy national security adviser during the George W. Bush administration. He also said it would keep the body count low, minimizing the sensational effect that terrorists aim for.

New York is just one city incorporating trauma-care teams into counterterrorism responses, said John D. Cohen, who until 2014 served as the counterterrorism coordinator at the Department of Homeland Security and is now a professor of criminal justice at Rutgers University, where he is the co-leader on a project examining mass-casualty attacks in the United States and Europe.

The Rescue Task Force is one of new counterterrorism elements designed bit by bit in New York since 2014, when the administration of Mayor Bill de Blasio moved in to City Hall.

Perhaps the most dramatic is the creation of heavily armed counterterrorism squads that are always ready: the Strategic Response Group and the Critical Response Command. There are now 2,000 police officers in New York equipped with long guns to confront terrorists head-on, versus 500 such officers three years ago.

Previously, trained officers had to be pulled off other assignments to respond to a mass shooting, taking crucial moments to change clothing and get the right equipment, find vehicles and converge from around the city. (The speed of the new approach was on display on June 30, when scores of officers converged on Bronx-Lebanon.)

Also, the first officer on the scene, whether on patrol or in plainclothes, now confronts the threat rather than backing off and radioing in details. So far, the department has trained 10,000 officers in active shooter response, adding more each day. They are trained to keep going until more heavily armed reinforcements, including officers from the Emergency Service Unit, arrive.

All that was in place when the violence erupted at Bronx-Lebannon, one of the city’s biggest and busiest.

“By and large, everything worked the way we’ve honed it toward,” said Miller of the Police Department, who responded to the hospital that day.

Of course, variables emerged. For one, Bronx-Lebanon is a high-rise with banks of elevators; the shooting played out on the 16th and 17th floors. Second, witness accounts indicated the gunman, Dr. Henry Bello, was moving upward and setting himself on fire.

Bello, 45, who had been what is called a house physician at the hospital, had been dogged by financial troubles and possibly addiction. Bello killed one person: Dr. Tracy Sin-Yee Tam, 32, who had volunteered to cover a colleague’s shift that day. Six others were wounded.

In the first moments of the attack, Bello’s moves mimicked the threat officials faced at the tabletop exercise that ended on June 1: a made-up scenario featuring a gunman, on the loose in a skyscraper, setting fires. (It ended, incredibly enough, just as the attack in Manila was getting underway.)

Patrol officers, counterterrorism teams and the nascent Rescue Task Force came together as planned, Miller said.

The first officers to arrive, from the 44th Precinct, ran inside and realized that people knew the identity of the attacker, who was believed to be hunting a particular person.

Those officers moved from floor to floor — as victims fled to various points after being wounded. As they went, they broadcast Bello’s name on the radio and distributed his photo over their smartphones.

“So that if someone encountered him, they would know he was the bad-guy doctor and not some other doctor,” Miller said.

Emergency Service Unit officers arrived and took over as fire and other police responders formed teams of 12, with officers surrounding emergency medical technicians.

“It was one of the first times, I think, in the nation, that rescue forces were activated in this fashion,” Leonard said.

Leonard said fire and police officers met and deemed “the bigger threat” to be the gunman — not the small fires he had apparently set. So firefighters were held back. If the fires had been more threatening, he added, officers would have escorted firefighters up.

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