Fifty-eight people were killed and 422 injured in October last year
The FBI is investigating a new "person of interest" in connection with the Las Vegas shooting, the county sheriff has said.
Stephen Paddock opened fire on concert-goers from his his 32nd-floor suite of the Mandalay Bay hotel on the Las Vegas strip, killing 58 people.
The sheriff of the Las Vegas Metropolitan Police Department said on Friday he does not foresee charges being filed against the girlfriend of Paddock, but added that the FBI was investigating a person he would not identify.
"We do not anticipate charges being brought forward against Marilou Danley," Clark County Sheriff Joseph Lombardo said, who oversees the Las Vegas police department, said as he announced the release of a preliminary investigative report.
Paddock is still believed to be the only suspect involved in the shooting, Lombardo said: "There was only one person responsible and that was Stephen Paddock."
Ms Danley said through her attorney on October 4th that she told the FBI she had no idea Paddock was "planning violence against anyone."
Her attorney could not immediately be reached for comment.
Ms Danley became a focus of the investigation for having shared Paddock's retirement community residence in Mesquite, Nevada, northeast of Las Vegas, before leaving for the Philippines in mid-September.
According to the police report, Ms Danley recalled Paddock behaving strangely during a stay at the Mandalay Bay in early September 2017.
The two were staying in room 60-235 and she observed Paddock constantly looking out the windows of the room which overlooked the Las Vegas Village venue, the report says.
Paddock would move from window to window looking at the site from different angles.
Ms Danley also described how Paddock's demeanour changed over the course of the last year as he became distant and germaphobic, the report said.
He also began to buy firearms and Ms Danley believed it was a hobby of his, the report says.
The report also said Paddock's primary care doctor described him as odd with little emotion, and said he may have been bipolar but Paddock would not discuss it and refused antidepressants.
Mr Lombardo said police still do not know why Paddock carried out the killings.
"This report is not going to answer every question or even answer the biggest question as to why he did what he did," he said.
He added that the 81-page preliminary report into the shooting also includes details of Paddock's "disturbing" search history on his computers, including his study of ballistics and SWAT tactics.
Police also recovered several hundred indecent images of children on Paddock's laptop, the report said.
FBI officials could not immediately be reached for comment.
Lombardo said 422 were injured by gunshots and the total number of injuries associated with the incident was 851.