(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.
Now, authorities are hoping to learn more about Stephen Paddock’s motive now that his girlfriend is in the country.
Marilou Danley arrived in Los Angeles from the Philippines Tuesday night and was met by the FBI. Authorities say she was not in the country during Sunday’s massacre, but is considered a person of interest.
Paddock and Danley lived together in a home roughly 80 miles away from where the shooting took place. That home is where authorities found more than a dozen firearms and thousands of rounds of ammunition.
The latest revelation came Tuesday afternoon when police said Paddock set up cameras inside his hotel suite and in the hallway on the 32nd floor of Mandalay Bay Resort and Casino. 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 murderer in modern U.S. 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 59 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.