(CNN) The work of identifying victims of the Las Vegas shooting and finding their families is far from over, according to US Sen. Catherine Cortez Masto.

"They are inundated" at the coroner's office, Cortez Masto, D-Nevada, said to CNN on Tuesday.

At least 58 people were killed and over 500 injured on Sunday, when Stephen Paddock, 64, fired repeatedly into a concert crowd from the 32nd floor of the Mandalay Bay Resort and Casino.

"It's a long, laborious process to identify the victims and reunite them with the family members," Clark County Sheriff Joseph Lombardo said Monday.

The Clark County coroner's office is getting an assist from cities that are no stranger to mass casualties: New York City and San Bernardino, California. A handful of experts from those places have joined county coroner John Fudenberg's team.

"They have experience, unfortunately, in this area," Fudenberg said of San Bernardino, where 14 people died in a shooting in December 2015.

As part of its operations, the coroner's office set up a 24-hour facility at the Las Vegas Convention Center to help families identify those who died, giving the team more space than is available at the their office, according to a statement Monday by the county.

There, investigators conduct interviews with families and gather identifying evidence such as dental records, photos and DNA.

"We've met with multiple families," Fudenberg said at a news conference Monday evening. By that point, all confirmed fatalities had been recovered from the scene and transported to the coroner's office. "We're working very hard at making those identifications."

"There are still families there that have not found their loved ones, and not for lack of trying," Cortez Masto said Tuesday, adding that the coroner was working around the clock.

"We're about as equipped as anybody in the country," Fudenberg said.

He quickly added, "I don't know that anybody can be fully equipped to handle this."

Behind the scenes

Responding to a mass shooting as a coroner or medical examiner can be straightforward -- but it isn't easy, said Dr. Michael Graham , chief medical examiner of St. Louis.

"Bodies are usually intact," Graham said, making them easier to identify than in a plane crash or bombing, but "moving and storage of the bodies can be an issue."

Medical examiners may identify the bodies in a number of ways: fingerprints, tattoos, clothing, DNA. In simpler cases, a person might be found with a driver's license. In others, people have been identified using implanted medical devices with unique serial numbers.

Some shootings, but not Las Vegas', might have a "closed roster," where investigators can match up names to bodies, said Kevin Lacy , the sheriff's captain assigned to the San Bernardino Coroner Division. There, the victims were county employees at Inland Regional Center.

But in Las Vegas, gunfire rained down on a crowd that numbered in the tens of thousands. Many of them were from elsewhere.

"The task of matching up the names of the deceased ... was far easier" in San Bernardino, Lacy said. "I wouldn't compare them. I wouldn't say it's even close."

Among the victims, potential causes of death may also be wider than gunshot wounds.

"There's a wide range of injuries, from gunshots to shrapnel wounds to trample injuries to people jumping fences, trying to egress and getting hurt," Clark County Fire Chief Greg Castle said at a news conference Monday evening.

But medical examiners do more than just identify bodies and causes of death, said Graham, who is also the past president of the National Association of Medical Examiners. They help law enforcement reconstruct what happened the night of the shooting.

For every victim, Graham's team will extensively document where the body is, what position it is in and even what path the bullets took.

In some cases, coroners will retrieve bullets for law enforcement so they can determine which gun was used. In other cases, bullets can break into fragments.

Authorities found 23 weapons in Paddock's Las Vegas hotel room, including a handgun and multiple rifles, some with scopes on them.

"There are all kinds of issues other than 'How did they die?' " Graham said.

Psychological impact

Orlando's chief medical examiner, Dr. Joshua Stephany, woke Monday morning and heard the news about Las Vegas. His heart sank.

In June 2016, Stephany was at the scene of a mass shooting hours after a gunman killed 49 and injured more than 50 others at the Pulse nightclub in Orlando. Before this week, the massacre at the LGBT club was considered the deadliest mass shooting in modern American history.

"It only took a year and a half for that title to go to another incident, unfortunately," he said.

Stephany knows how painstaking it can be to work at a mass-casualty crime scene -- to identify bodies and transport them, to get endless calls from families looking for their sons and daughters, asking whether they suffered. Knowing this firsthand, he sent Fudenberg an email of support.

"He just joined a very exclusive club that no one wants to be a part of," Stephany said.

He knows the added difficulty that can come from working on mass shootings, beyond the heavy case load and tiered investigations. There's a psychological component, too.

With the Pulse shooting, which took place at a gay club, Stephany had to think of his staff members: Did any of them frequent the club? Did they know the victims? Did they have any personal ties to the bodies they were about to investigate?

"I had to worry about whether the personal connections were there," he said.

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Although medical examiners might see grisly scenes all the time, it's the staggering number of victims and amount of violence that can take its toll on those who show up after a massacre has occurred, Graham said.

"There's no break," he said. "You have no emotional relief."

For that reason, Stephany has not followed the news from Las Vegas as closely as others. "It's a little too raw still," Stephany said.

This article has been updated to reflect a change in the victim death toll.