Clark County Sheriff Joe Lombardo says he anticipates holding a news conference in about a week regarding the investigation into the deadliest mass shooting in recent USA history but that he doesn't expect the update to include shooter Stephen Paddock's motive.
The document says Danley also provided a DNA sample to authorities.
They had been sealed for months, but lawyers for several media companies, including the Los Angeles Times, argued for the release of the information.
Las Vegas Police Officer Aden Ocampo Gomez and Federal Bureau of Investigation spokeswoman Sandra Breault said Friday that they had no update about Paddock's motive.
Paddock, firing from his high-rise hotel suite at the Mandalay Bay resort, killed 58 people and injured hundreds of others at a country-music festival on the Las Vegas Strip far below before killing himself, police said.
"Try an ar before u buy. Located in the las vegas area", reads one email.
"We have a wide variety of optics and ammunition to try", another email sent the same day said.
An email in response suggested trying a bump stock on a 100-round magazine rifle, saying it would be "a thrill".
The newspaper also said investigators identified an email inbox belonging to Paddock that contained a message from a Gmail account officials believe was related to Paddock's preparations for the attack. An FBI investigator reportedly said in one of the documents that "investigators need to determine who was communicating with him about weapons that were used in the attack". Police searched Paddock's room, his vehicle, and two homes he owned in Reno and in Mesquite, Nevada, where they found a cache of weapons.
Danley told authorities they would probably find her fingerprints on bullets because she sometimes helped Paddock load ammunition magazines.
The FBI agent who prepared the affidavit noted that Danely was cooperating with investigators and that the investigation "to date has not produced any conclusive evidence that Danely aided Paddock, had foreknowledge of his plans or has been deceptive with law enforcement".
It is unclear what has transpired with respect to Danely since the affidavit was written on October 7.
Microsoft and Facebook did not immediately respond to emails and calls from Reuters on Friday night.
Documents posted online by the Review-Journal showed that Federal Bureau of Investigation agents sought information from Microsoft and Facebook regarding accounts held by Paddock and Ms Danley.
An affidavit notes that Danely's Facebook account was deleted hours after the attack. Investigators were only able to search one but could not unlock the others.