A federal judge in Nevada unsealed hundreds of pages of FBI documents about the Las Vegas massacre Friday, giving new insight into the gunman and the months leading up to the deadly mass shooting.

The documents, which were released in response to several media lawsuits, include more than a dozen search warrant affidavits.

They reveal that gunman Stephen Paddock exchanged emails about buying rifles and bump stocks months before he killed 58 people and wounded more than 500 others when he opened fire on a crowd from a hotel room in October.

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

"We have a huge selection in the las vegas area," the message read.

Paddock replied saying that he wanted to test several scopes and different types of ammunition.

An email in response suggested trying a bump stock on a 100-round magazine rifle, saying it would be "a thrill."

Paddock's personal email address and the Gmail address had similar names, leading investigators to suspect he may have been emailing himself, but don't understand why.

The documents also reveal that Paddock's girlfriend, Marilou Danley, had personally handled the stockpile of ammunition found in his home.

Danley told authorities they would probably find her fingerprints on bullets because she sometimes helped Paddock load ammunition magazines.

An FBI agent told a judge on Oct.3 that Danley cooperated with police and there was no evidence at that time of "criminal involvement."

However, the agent said authorities hadn't ruled her out as a person of interest.

Police and the FBI have said they found no evidence that Paddock had help carrying out the attack.

One of the warrants describe the extent to which Paddock went to conceal his actions, saying he "destroyed or tried to hide digital media devices."

Authorities said he used anonymous communications devices, including a prepaid cellphone, to throw off any police investigation.

"Paddock planned the attack meticulously and took many methodical steps to avoid detection of his plot and to thwart the eventual law enforcement investigation that would follow," the FBI said.

The search warrants show authorities found three cellphones belonging to Paddock in his room at the Mandalay Bay Resort and Casino. Investigators were only able to search one and could not unlock the others.

One agent wrote that he believed "if there were any information related to a potential conspiracy, it would be found within" the locked phones.

Investigators also revealed that Mr. Paddock may have been treated for "unidentified medical conditions." After the shooting, Danley told investigators that Paddock's physical and mental health seemed to have deteriorated in recent months.

Authorities still do not know Paddock's motive for the attack and the investigation is still ongoing.

A Nevada court will hear arguments on Tuesday about whether Las Vegas police search warrant documents should remain sealed or released to the public.