By GRAHAM RAYMAN

It began with a panicked 911 call from a woman at Bronx-Lebanon Hospital routed to NYPD Operator Joann Tindal.

Gunfire had erupted on the 16th floor. As the caller cowered in her dad’s hospital room, deranged ex-medical technician Henry Bello roamed the floor. He was armed with a rifle and on the hunt.

For the next 11 wrenching minutes, Tindal patiently talked her through the chaos.

Stay calm, stay quiet, the 911 operator told the woman. Lock the door. Keep everyone in the room.

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“You can stay on the phone with me if you want,” Tindal recalled telling the woman.

“There were other people in the room with her and I was telling her to reassure them that help was on the way,” she told the Daily News. “This was the first time I had a call like that.”

In another part of the sprawling 911 call center at 11 MetroTech in downtown Brooklyn, Special Operations Dispatcher Michele Gambrell got the message over her computer of the unfolding horror.

“10-10. Shots fired, unconfirmed. Bronx-Lebanon,” she said over the air.

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Then another call came in. And a third. And then a fourth. All from three different numbers in different parts of the hospital. In all, at least 40 emergency calls were made from the hospital.

After 13 years on the job, Gambrell knew an active shooter was on the loose, and began transmitting the information Emergency Service Unit officers who were on their way to the scene.

“When I looked at the location and saw that they were all valid numbers from the same location giving the same information, I told my supervisor, this is real,” Gambrell told The News.

“I was shocked, but at the same time, you kind of get in the zone, you get focused where like everything else is blacked out around you,” she said. “I only hear what I need to hear.”

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Gambrell, 36, and Tindal, 46, played key roles in coordinating the emergency response to the June 30 hospital shooting that left seven people shot and one dead. They represent the unsung backbone of the NYPD.

They are two of the 1,600 or so people in the NYPD’s communications division, responsible for dealing with people often in the midst of the worst crises of their lives, and relaying critical information to cops in situations where every second counts.

The center receives about 10 million calls for service a year – for everything from repeated caller “Miss Ann” who just wants to know the date and time to the panicked teen, who reached Gambrell early in her career, and told her that his stepfather was killing his mother. And there was the suicidal man Tindal talked out of killing himself.

In the truly high-octane moments, like the Bronx-Lebanon shooting, it falls to them, no matter their own feelings, to remain calm as they receive information and direct police to the scene.

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“I like to say if you save one life, you’re a hero, but if you save 100, you’re a 911 operator,” said Deputy Chief Richard Napolitano, commanding officer of the Communications Division. “They never know what’s on the other end of that phone.”

Napolitano recalled listening in as a different dispatcher talked a suicidal man out of jumping in front of a train by referring to a rough period in her own life and sympathizing with him.

Gambrell and Tindal typically deal with about 100 calls a day and make a base salary of about $49,500 a year. A police officer by comparison makes $85,292 after five years.

The operators and dispatchers, sit at consoles on day tour in a big open room with large windows, three screens in front of them and a device that allows them to replay snippets of calls in case they need to check a fact.

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For such an intense job, the floor was surprisingly quietly on a recent visit to the call center.

Behind them supervisors watch the calls as they develop, often listening in to make sure the correct personnel are being dispatched.

The soft-spoken Tindal, a mom with two grown kids from Jamaica, Queens, was working as a paraprofessional for the city schools in 2000 when she decided she needed a job that paid a little better because she had two young kids.

She took the test and started work. On Sept. 11, 2001 – her birthday – she found herself taking 911 calls from people trapped in the burning towers of the World Trade Center.

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The chattier Gambrell, raised in Bensonhurst, Brooklyn, was 23 in 2003 and mulling a career as a cop or a soldier. A family friend who was a dispatcher suggested she apply.

“I felt like I’m sort of an officer but in the safe part, behind the scenes,” she said. “When they are running to a job, I feel like I’m running with them. I like the adrenaline.”

They have both developed thick skin – a requirement of a job where it’s routine for callers to yell or scream into the phone.

“After a while, you get that tough skin, and even though something is sad and tragic you just can’t go home and think of it that way,” said Gambrell, who imagines them as her grandfather and treats them that way. “You have to think of it like you helped someone today.”

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Adds Tindal, “You have to be an equal amount compassionate, but also tough at the same time to do the job.”

Cops too can sometimes get a bit heated responding to an emergency.

“They usually are never rude to me, but if they do get snippy, I am still respectful. I look at them like they’re my children and I want to keep them safe.”

And then there are the calls like those from people like “Miss Ann,” who rings often and seems to just want someone to talk with.

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“I usually tell her ‘Ma’am, when you do have an emergency please call us,’” Tindal said. “But there was one day when she was calling a lot, so I put in a call for a unit to go over and check on her.”

Gambrell and Tindal cope with the job’s challenges by trying to leave it in the building.

“Usually when I go home, I watch the news and I’ll say to my daughter, ‘Oh I had a call on that today,’ but I don’t really talk about it,” Tindal said.

Gambrell says, “When I walk out of those doors, it’s like a switch has been flipped. A calm comes over me. If I went home and thought about it every day, I would be a basket case.”

When she went home after dealing with the hospital shooting, Gambrell felt proud.

“I felt like I did a good job,” she said. “Those people got helped, and the officers knew where to go when they got there.”

This article was originally published in the New York Daily News on August 5, 2017.