As the deadliest mass shooting in American history unfolded in Orlando early Sunday morning, Matthew Gentili was staffing the phones less than two miles away.

As Omar Mateen terrorized Pulse, a popular gay club, the phones at News 13 began to ring.

Gentili, a producer at the television station — just a five-minute drive from Pulse on South Orange Avenue — spoke to one frightened Floridian after another.

“I was receiving phone calls from viewers saying, ‘What’s going on? What’s happening?'” Gentili told a reporter at his own station Tuesday.

When the phone rang once more at around 2:45 a.m., Gentili answered as he had all night: “News 13, this is Matt.”

But this call was different.

This call was chilling.

“Do you know about the shooting?” a man asked Gentili.

“Yes, I’m getting calls,” Gentili said. “I am hearing reports of a shooting. …”

The man cut him off.

“I’m the shooter. It’s me,” the man said. “I am the shooter.”

The caller then said he had carried out the Pulse attack for the Islamic State and began speaking quickly in a foreign language.

“At the time, I didn’t know what he was saying,” Gentili told News 13 reporter Scott Fais. “He was speaking so fast. But it was … he was speaking fluently. Whatever language he was speaking, he knew it. And he was speaking it very quickly. And that is when I said to him, ‘Sir. Please. Speak in English, please.'”

“I did it for ISIS,” the caller said, according to Gentili, “I did it for the Islamic State.”

When the TV producer asked the caller’s location, the man said it was “none of my [expletive] business,” Gentili said.

“It was silent for a while,” Gentili said. “I asked him: ‘Is there anything else you want to say?'”

The man said no and hung up.

After the call, Gentili quickly plunged back into producing news about the mass shooting, in which Mateen killed 49 people and injured 53 more, according to authorities. When he finally did get off work, he was interviewed by the FBI about the phone conversation.

The gunman who killed at least 49 people in a shooting rampage at an Orlando nightclub has been identified as 29-year-old Omar Mateen. Here is what we know about him so far. (Deirdra O'Regan/The Washington Post)

FBI agents would not confirm whether it was the gunman on the phone with the producer, but the TV station’s managing editor matched the incoming phone number to Mateen, according to News 13.

The timing and content of the phone call also appears to make sense.

After opening fire within the club at around 2 a.m. Sunday morning, Mateen then called 911 for the first time at 2:30 a.m. but quickly hung up without saying anything, FBI Director James Comey said at a briefing Monday. Mateen then called back, spoke briefly with the 911 dispatcher and hung up again. The dispatcher called back, and they had a second brief conversation.

“During the calls he said he was doing this for the leader of [the Islamic State] who he named and pledged loyalty to,” Comey said. He said the gunman also expressed solidarity with the perpetrators of the Boston Marathon bombing and with Moner Mohammad Abusalha, a Florida man who in 2014 became a suicide bomber in Syria.

The phone call to News 13 came shortly after that second 911 conversation ended.

Omar Mateen showed no signs of remorse in phone calls with police during an hours-long standoff at the Pulse nightclub, Orlando Police Chief John Mina said in an interview with The Washington Post on June 13. (Gillian Brockell,McKenna Ewen/The Washington Post)

Roughly two hours later, Orlando police, worried by Mateen’s comments about explosives, decided to stage a rescue of the remaining club-goers. Police used an armored vehicle to ram the nightclub. As terrified hostages escaped from the hole in the building, so, too, did Mateen.

He was armed with two guns and died in a hail of police gunfire.

Two days later, Gentili said he was still haunted by the phone call.

“I will never forget the words he said to me,” Gentili told News 13.

“I’m definitely changed,” he also said Tuesday. “When you get a phone call like that, I’m never going to be able to answer the phone again without thinking this is the most serious call I’ll ever get in my life.”

Read more about the Orlando mass shooting:

‘The guilt of being alive is heavy,’ survivor of nightclub shooting says

Orlando shooter’s wife facing intense scrutiny from the FBI

The lives lost in Orlando