Las Vegas police outside the Mandalay Bay complex early Monday. (Buck/Epa-Efe/Rex/Shutterstock)

Reporter Rachel Crosby was getting ready for bed Sunday night when a group text message from her editor lit up her phone.

"Report of two active shooters at Mandalay Bay," wrote her boss, Carri Geer Thevenot. "Who is available to help?"

Within moments, Crosby was on her way to University Medical Center, a few blocks from her apartment north of the Las Vegas Strip. There she encountered the first signs of an unfolding tragedy. She saw a bewildered trauma-room nurse, on a brief respite, fall to his knees as he spoke into his phone. "Jesus," she overhead him say. "It's bad."

A few minutes later, as Crosby began calling people in local law enforcement, she learned just how bad it was. "#breaking," she tweeted just after midnight local time. "A police source just confirmed to me that more than 20 people are dead."

In the immediate aftermath of what has turned out to be the deadliest mass shooting in recent American history, Las Vegas's leading newspaper, the Review-Journal, became the eyes on the episode for much of the world. The paper quickly confirmed from law enforcement that there was only one shooter involved and that he had killed himself after inflicting a grievous toll on people attending a country music festival across from the Mandalay Bay Resort and Casino. Crosby's initial report of 20 soon spiraled past 50. By Monday morning, authorities said the figure was 58 dead, with more than 500 injured.

The paper marshaled about 50 of its 140 journalists Sunday night and dozens more on Monday, said Editor in Chief Keith Moyer. In addition to scoops — Moyer's sister, a freelance writer in Florida, fed the first interview with shooter Stephen Paddock's brother to the paper — the Review-Journal treated the episode as a community emergency, directing readers to blood banks and centers where people could find information about lost relatives and victims.

The paper reacted so quickly to the first police scanner reports of a shooting that one of its reporters was inside the Mandalay Bay complex when police declared it part of the crime scene and locked it down, temporarily preventing people from leaving.

"It was pretty seamless," Moyer said during a brief break in directing coverage Monday. "I'm really proud of what we produced."

Newspaper reporting staffs have been decimated by the rise of the Internet, but the shooting was again a validation of what they do best, Moyer said. Despite staff turnover in recent years, the Review-Journal still maintains the largest newsroom in the state, he said, and with it direct connections to city and county health, law enforcement and emergency-response officials.

He suggested the paper's reporting of the shooting may counter the narrative that sprang up around it after Las Vegas casino magnate Sheldon Adelson bought it in late 2015.

Adelson's $140 million purchase was first beset by mystery and then by conspiracy whispers. The buyer was initially identified only as a Delaware shell company fronted by a Connecticut man named Michael Schroeder. Adelson and his family did not acknowledge that they were behind the shell company until Fortune magazine and the Review-Journal itself reported their involvement.

The acquisition then set off fears that Adelson — the largest donor to the Republican Party during the 2012 and 2016 cycles and Donald Trump's leading contributor in 2016 — would use the paper to influence statewide politics and to benefit Adelson's Las Vegas Sands Corp.

On Monday, Moyer said: "Sheldon Adelson doesn't have anything to do with our coverage. People thought he was dictating our coverage. We don't hear from Sheldon Adelson." (Moyer also distanced his news staff from one of the paper's columnists, syndicated radio host Wayne Allyn Root, who without evidence speculated on Twitter about a "Muslim" connection to the shooting).

Adelson has brought additional resources to the paper, increasing its newsroom from about 90 journalists when Moyer started 19 months ago to about 150.

Some of that additional reporting muscle may have paid off during the trauma and tragedy of Sunday's mass killing. The paper published stories, photos and videos that were widely shared online, including a concertgoer's video of the scene as automatic gunfire rains down.

The Review-Journal typically gets about 3 million unique visitors to its website per month; between late Sunday night and midmorning Monday it had attracted 465,000 people, a 635 percent increase over its usual traffic during that period, according to the paper.

Crosby, the reporter, said she was in "work mode" and "numb" for most of the night as she reported the story. When details about the shootings were still emerging, she said, she texted her colleagues to "take a couple of deep breaths, watch your surroundings, and know where the exits are."

However, by Monday morning, returning to her apartment after a sleepless night, she was spent, physically and emotionally. She tweeted this: "Just want to add that [the Las Vegas Metropolitan Police Department] was kind enough to let me use the restroom inside HQ. Finally got a second to cry."