Unsealed documents have been released, which reveal more about Stephen Paddock and his Aussie girlfriend before he carried out America's deadliest mass shooting.

Sealed documents have been released for the first time, which shed more light on what Las Vegas killer Stephen Paddock was up to before he carried out America's deadliest mass shooting, said news.com.au.

FBI agents knew Paddock left behind big caches of guns, ammunition and explosives when they sought warrants to search his properties and online accounts, according to the court documents.

Video from a neighbouring building has shown the spot that Stephen Paddock chose to fire onto the concert goers. Source - @NewYork_SPIN

A US judge in Nevada unsealed the documents showing some of what federal agents learned about him in the week after the Las Vegas shooting.


Prosecutors didn't oppose the request from media organisations including The Associated Press to release affidavits that were filed to get search warrants.

The police learned that Paddock had exchanged emails about buying rifles and bump stocks months before he carried out the mass shooting using guns equipped with the device that allows semiautomatic weapons to fire nearly as fast as automatic ones.

The documents said Paddock had received an email from a Gmail account in July last year, encouraging him to try an AR-style rifle before buying one.

It said, "we have huge selection" in the Las Vegas area.

Paddock wrote back that he wanted to try several scopes and different types of ammunition. An email in response suggested trying a bump stock on the rifle with a 100-round magazine.

Paddock's email address and the Gmail address had similar names. Investigators say they suspect he may have been emailing himself, but couldn't figure out why.

The documents also show that agents sought the email, Facebook and Instagram accounts of Paddock's girlfriend, Marilou Danley, who was in the Philippines during the October 1 shooting that left 58 people dead and hundreds of others injured before he killed himself.

The girlfriend of the Las Vegas shooter told authorities that they would likely find her fingerprints on some of Stephen Paddock's bullets because she sometimes assisted him in loading ammunition into magazines.

While there was no evidence at that time of "criminal involvement" by Danley, an October 3 document showed, it noted that investigators had not ruled out the possibility.

Leaked photographs from inside the hotel room used by Las Vegas shooter Stephen Paddock in the Mandalay Bay Hotel showing his arsenal of weapons. Photo / Twitter
Leaked photographs from inside the hotel room used by Las Vegas shooter Stephen Paddock in the Mandalay Bay Hotel showing his arsenal of weapons. Photo / Twitter

Investigators have said that Paddock meticulously planned his attack and intentionally concealed his actions.

He modified assault-style rifles to shoot rapidly, set up cameras to watch for police outside his hotel room and wounded a security guard in the hotel hallway.

Investigators found no evidence that Paddock had help carrying out the attack.

Paddock's three-bedroom house in a retirement community in the city of Mesquite was searched twice — first by police and FBI agents in the hours immediately after Paddock was identified as the shooter.

Clark County Sheriff Joe Lombardo later said that October 2 search found 19 guns and several pounds of potentially explosive materials.

The FBI returned to the house a week later for what officials called "redocumenting and rechecking."

Officers also raided Paddock's hotel suite where he opened fire and searched his vehicle after it was found parked in the casino parking structure. Lombardo said several pounds of ammonium nitrate, a material used to make explosives, was found in the car.

Other searches were conducted at a house the gunman owned in Reno where agents found a red SUV. A neighbour reported that Paddock kept a safe the size of a refrigerator in the garage.

FBI agents also returned to that house, on October 10, after local police determined someone had broken in days earlier.

However, the documents didn't answer the key unanswered question: What motivated a 64-year-old high-stakes gambler to unleash gunfire from his room on the 32nd floor of the Mandalay Bay resort into an outdoor concert below?

Stephen Paddock adapted his semi-automatic weapons to fire as a fully automatic gun using a bump stock. Video / Boston25

Las Vegas police Officer Aden Ocampo Gomez and FBI spokeswoman Sandra Breault said that they had no update about Paddock's motive. Both called it an ongoing investigation.

A Nevada judge is due to hear arguments Tuesday about whether Las Vegas police search warrant documents should remain sealed.