(CNN) Every detail of this indiscriminate mass murder seemed meticulously planned.

The selection of a hotel room overlooking a music festival, days before the attack. The cache of 23 weapons inside the gunman's Las Vegas suite. And thousands of rounds of ammunition -- plus an ingredient used in explosives -- inside the killer's home and car.

The latest revelation came Tuesday afternoon when police said gunman Stephen Paddock set up cameras inside his hotel suite and in the hallway. Police are not aware whether the devices were transmitting -- the FBI is investigating their use -- but the Clark County sheriff told reporters he thinks the shooter might have used them to watch for people approaching his room.

One camera looked out the peephole on the suite's door.

The Bureau of Alcohol, Tobacco, Firearms and Explosives disclosed that Paddock had outfitted 12 of his rifles with a legal device called a bump-fire stock, which enables a shooter to fire bullets rapidly, similar to an automatic rifle.

Authorities released the first body camera footage of police responding to the shooting. It captured the rapid staccato of the gunfire at a fairly close range.

Officers were seen hunkering down behind a wall. "Go that way, get out of here! There's gunshots coming from over there," one officer is heard yelling at civilians. At one point, they were next to a patrol vehicle on Las Vegas Boulevard, where one officer was shot, Undersheriff Kevin McMahill said.

No one knows why Paddock morphed from a retired accountant to the deadliest mass shooter in modern US history. His relentless gunfire -- police say he fired for nine to 11 minutes after the first 911 call -- on country music fans at an outdoor concert left 58 people dead.

Another 500 people are still trying to recover from injuries -- everything from gunshot wounds to stampede injuries suffered when 22,000 people tried to flee the gunman's aim.

So far, police believe Paddock acted alone -- which could make the motive harder to determine.

Photos published by the Daily Mail of the United Kingdom show a body inside Stephen Paddock's room at the Mandalay Bay.

Latest developments

Stephen Paddock

-- Paddock's girlfriend, Marilou Danley arrived at LAX on Tuesday night, and is being accompanied by the FBI in Los Angeles, a law enforcement source told CNN. Danley flew from Manila, said Maria Antoinette Mangrobang, a spokeswoman for the Bureau of Immigration in the Philippines. Danley had entered the Philippines in September 15, and again on September 25, traveling on her Australian passport, she said. There has been communication between authorities in the Philippines, the FBI and US Department of Homeland Security, Mangrobang said.

-- Clark County Coroner John Fudenberg said that 58 people were killed. Authorities had previously said 59 were killed in the shooting, but on Tuesday clarified that number included the shooter.

-- The Daily Mail newspaper of the UK has published several photos taken in Paddock's room after the shooting. In one photo, the legs of a dead shooter can be seen on the floor. The photos show semiautomatic assault-style rifles on the floor and on furniture. Stacks of ammunition magazines used in rifles can also be seen.

-- Paddock wired $100,000 to the Philippines, a law enforcement source said. However, officials haven't able to see yet precisely when the wire happened or who was the recipient. The FBI is working with Filipino authorities to determine details.

-- President Donald Trump tweeted: "It is a 'miracle' how fast the Las Vegas Metropolitan Police were able to find the demented shooter and stop him from even more killing!"

-- Five handguns, two shotguns and a "plethora" of ammunition were found in Paddock's Verdi, Nevada, property, police said. Authorities previously found 42 guns in Paddock's hotel room and at his Mesquite, Nevada, home.

A photo published by the Daily Mail shows long guns, a hammer and a stack of magazines for rifles.

'I felt him get shot in the back'

JUST WATCHED Shooter's angle prevented people from escaping Replay More Videos ... MUST WATCH Shooter's angle prevented people from escaping 02:06

Heather Melton heard the noise interrupting the concert and told her husband, Sonny, she thought it might be gunfire. He, like most people, thought it was fireworks.

Then the bullets started ricocheting off the ground around the Tennessee couple. She wanted to get low; he said, no, we'll get trampled.

So they ran, away from the gunfire, Sonny just behind Heather, until he was felled by a bullet.

"I felt him get shot in the back," she told "Anderson Cooper 360." There were bodies all over the ground.

Several rifles are on two chairs pushed together while several lie on the floor, a photo obtained by the Daily Mail shows.

"I was trying to talk to him and he wasn't responding," said Heather, an orthopedic surgeon. She said she got over him and started doing CPR. People said to get down. Sonny, a registered nurse, was bleeding from the mouth.

"If he was one of the people who had survived, ... he would've been one those people running back in" - Wife of shooting victim Sonny Melton pic.twitter.com/fX0m7ksNjG — Anderson Cooper 360° (@AC360) October 4, 2017

Heather Melton said she knew he probably was gone, but she wanted to hope.

Sonny was declared dead at the hospital.

"He was the most selfless person that I ever met, and even until his last breath he proved that," Heather said.

The investigation

Paddock's violent transformation has mystified everyone -- his brother , investigators and the families he victimized.

Police had no prior knowledge of the gunman before the attack. "I don't know how it could have been prevented," Lombardo said.

The massacre has no known link to overseas terrorism or terror groups, a US official with knowledge of the case said. And authorities say it's too early to tell whether the killings were an act of domestic terrorism.

"We have to establish what his motivation was first," Lombardo said.

For an act to be considered terrorism, it must appear that it was intended to intimidate or coerce a civilian population, or try to influence political change.

The gunman's brother, Eric Paddock, said he was "completely befuddled" by his brother's actions.

He said Stephen Paddock was an avid gambler who had "no history of violence. No history of anything -- couldn't give a s*** less about politics, religion, pointy hatted people, etc, etc. He just wanted to get a freaking royal flush."

On Tuesday, Paddock's family sent condolences to the victims.

"There are no words to describe the sadness we feel for those who lost their lives in this tragic event. Please know that you are in our prayers and that our hearts are heavy for the families who have been left heartbroken and without answers," the family said in a statement.

Running back into danger

The massacre started at about 10 p.m. Sunday at the Route 91 Harvest festival , Sheriff Lombardo said.

Country singer Jason Aldean was on stage when bullets started raining onto the crowd.

Photos: Mass shooting at Las Vegas music festival Debris is scattered on the ground Monday, October 2, at the site of a country music festival held this past weekend in Las Vegas. Dozens of people were killed and hundreds were injured Sunday when a gunman opened fire on the crowd. Police said the gunman fired from the Mandalay Bay hotel, several hundred feet southwest of the concert grounds. It is the deadliest mass shooting in modern US history. Hide Caption 1 of 30 Photos: Mass shooting at Las Vegas music festival Broken windows of the Mandalay Bay are seen early in Las Vegas on Monday. Police said the gunman fired on the crowd from the 32nd floor of the hotel. Hide Caption 2 of 30 Photos: Mass shooting at Las Vegas music festival People cross a street near the Las Vegas Strip just after sunrise on Monday. Thousands were attending the music festival, Route 91 Harvest, when the shooting started. Hide Caption 3 of 30 Photos: Mass shooting at Las Vegas music festival People embrace outside the Thomas & Mack Center after the shooting. Hide Caption 4 of 30 Photos: Mass shooting at Las Vegas music festival Police arrive at the Sands Corporation plane hangar where some people ran to safety after the shooting. Hide Caption 5 of 30 Photos: Mass shooting at Las Vegas music festival A woman cries while hiding inside the Sands Corporation plane hangar. Hide Caption 6 of 30 Photos: Mass shooting at Las Vegas music festival Concertgoers dive over a fence to take cover from gunfire on Sunday night. Hide Caption 7 of 30 Photos: Mass shooting at Las Vegas music festival Police take position outside the Mandalay Bay. Hide Caption 8 of 30 Photos: Mass shooting at Las Vegas music festival A man lays on top of a woman as others flee the festival grounds. The woman reportedly got up from the scene. Hide Caption 9 of 30 Photos: Mass shooting at Las Vegas music festival Hide Caption 10 of 30 Photos: Mass shooting at Las Vegas music festival People are seen on the ground after the gunman opened fire. Hide Caption 11 of 30 Photos: Mass shooting at Las Vegas music festival People run from the festival grounds. Hide Caption 12 of 30 Photos: Mass shooting at Las Vegas music festival A woman is moved outside the Las Vegas Tropicana resort. Multiple victims were being transported to hospitals in the aftermath of the shooting. Hide Caption 13 of 30 Photos: Mass shooting at Las Vegas music festival People are searched by police at the Tropicana. Hide Caption 14 of 30 Photos: Mass shooting at Las Vegas music festival An ambulance leaves the intersection of Las Vegas Boulevard and Tropicana Avenue. Hide Caption 15 of 30 Photos: Mass shooting at Las Vegas music festival A man in a wheelchair is evacuated from the festival after gunfire was heard. Hide Caption 16 of 30 Photos: Mass shooting at Las Vegas music festival Victims of the shooting are tended to in the street. Hide Caption 17 of 30 Photos: Mass shooting at Las Vegas music festival Concertgoers help an injured person at the scene. Hide Caption 18 of 30 Photos: Mass shooting at Las Vegas music festival People gather around a victim outside the festival grounds. Hide Caption 19 of 30 Photos: Mass shooting at Las Vegas music festival A couple huddles after shots rang out at the festival. Hide Caption 20 of 30 Photos: Mass shooting at Las Vegas music festival An injured woman is helped at the Tropicana. Hide Caption 21 of 30 Photos: Mass shooting at Las Vegas music festival Police and emergency responders gather at the intersection of Las Vegas Boulevard and Tropicana Avenue. Hide Caption 22 of 30 Photos: Mass shooting at Las Vegas music festival A police officer takes position behind a truck. Hide Caption 23 of 30 Photos: Mass shooting at Las Vegas music festival A crowd takes cover at the festival grounds. Hide Caption 24 of 30 Photos: Mass shooting at Las Vegas music festival Police officers advise people to take cover in the wake of the shooting. Hide Caption 25 of 30 Photos: Mass shooting at Las Vegas music festival People tend to a victim at the festival grounds. Hide Caption 26 of 30 Photos: Mass shooting at Las Vegas music festival Police stand at the scene of the shooting. Hide Caption 27 of 30 Photos: Mass shooting at Las Vegas music festival A woman sits on a curb at the scene of the shooting. Hide Caption 28 of 30 Photos: Mass shooting at Las Vegas music festival Police are deployed to the scene. Hide Caption 29 of 30 Photos: Mass shooting at Las Vegas music festival A man makes a phone call as people run from the festival grounds. Hide Caption 30 of 30

"On the main floor ... there was no cover -- they were all exposed," survivor Rusty Dees said. "So you didn't know if somebody was shot or if they were laying down."

Frantic concertgoers piled on top of each other, trying to get out of the line of fire. But an off-duty nurse ran back into the danger to help those who had been shot.

"We went back because I'm a nurse and I felt I had to," she told CNN affiliate KTNV . "I went to three different scenes, and by the time I got to the third one, there was just dead bodies."

The nurse said she was far from alone.

"There was so many people, just normal citizens, doctors, cops, paramedics, nurses, just off-duty. Everyone was just communicating and working together."

JUST WATCHED Random acts of heroism save lives in Las Vegas Replay More Videos ... MUST WATCH Random acts of heroism save lives in Las Vegas 02:04

Corrine Lomas recalled the heroism of fellow concertgoers.

"A lot of really good people (were) holding people's wounds shut, trying to help them while everybody was just ducked down," she said.

$8.1 million raised

Countless strangers have rallied to support victims, donating blood, money and supplies.

By Tuesday evening, a GoFundMe page started by a Clark County commissioner had raised more than $8.1 million.

"Funds will be used to provide relief and financial support to the victims and families of the horrific Las Vegas mass shooting," county commission chair Steve Sisolak wrote.

Throngs of blood donors lined up for hours to help the wounded.

JUST WATCHED Survivor held stranger's hand as he died Replay More Videos ... MUST WATCH Survivor held stranger's hand as he died 02:00

"This is America -- people coming together, helping out." Hector Salas tweeted . "Likely more than 1000 people waiting in line to donate blood.

Strangers also donated flights, housing, food and transportation to victims' relatives coming to Las Vegas, Clark County Fire Chief Greg Cassell said.

"It takes the worst of America to also see the best of America," said Dees, who survived the gunfire. "Everybody was helping each other."

Correction: An earlier version of this story incorrectly identified the name of survivor Rusty Dees.