A US judge in Nevada unsealed the documents showing some of what federal agents learned about Stephen Paddock in the week after the Las Vegas shooting.
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.
Investigators continue to search for Stephen Paddock's motive; Trace Gallagher reports from Los Angeles. An FBI spokeswoman in Las Vegas declined comment on the documents on Friday evening.
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.
An FBI special agent wrote in one affidavit seeking a search warrant that "the methodical nature of the planning employed by Paddock, coupled with his efforts to undermine the preceding investigation, are factors indicative of a level of sophistication which is commonly found in mass casualty events such as this".
Authorities also recovered 18 firearms and more than 1,000 rounds at Paddock's house in Mesquite, Nev.
She told investigators she occasionally helped Mr Paddock load magazines.
The search warrants also covered electronic accounts and social media accounts of Paddock and Danley.
Authorities released Paddock's name about an hour after Danley deleted her account.
Documents posted online by the Review-Journal showed that Federal Bureau of Investigation agents sought information from Microsoft and Facebook regarding the accounts held by Paddock and Danley.
Esperanza Mendoza, a supervisor at the Starbucks, told The Times in October: "He would glare down at her and say - with a mean attitude - 'You don't need my casino card for this". The Las Vegas Review Journal and CNN were among the media outlets filing suit for the documents' unsealing. "Located in the Las Vegas area".
Later that day another email read: "We have a wide variety of optics and ammunition to try".
The emails also mentioned trying out an AR-style rifle before purchasing one.
In the affidavit, investigators said they believed the communications may have been related to the eventual attack.
It is not known who the latter email account belongs to. There is a mention of Paddock's health in one affidavit, with an Federal Bureau of Investigation agent saying that he "may have been treated for yet unidentified medical conditions", but the agent does not elaborate. Receiving a search warrant for that account "will lead investigators to determine the full scope of Stephen Paddock's plan", an F.B.I agent wrote to the judge.