Without having found a motive for October's mass shooting at the Route 91 Harvest Festival in Las Vegas, Nev., officials are closing their investigation of the tragedy. Clark County Sheriff Joe Lombardo announced the news at a press conference on Friday (Aug. 3).

On Oct. 1, 2017, a gunman opened fire from a hotel room on the 32nd floor of the Mandalay Bay hotel onto the crowd gathered for the Route 91 Harvest Festival. Jason Aldean was in the middle of his headlining and festival-closing set when the shooting began. Fifty-eight people were killed, and more than 800 more were injured; the gunman, 64-year-old Stephen Paddock, then killed himself.

"What we have been able to answer are the questions 'who,' 'what' 'when' and 'how,'" Lombardo said at the press conference (quote via Buzzfeed). "What we have not been able to definitively answer is the 'why'."

A lengthy, 181-page report, released on Friday, explains that police looked into Paddock's financial history and actions prior to the shooting while trying to determine a motive. They spoke with a number of people connected to him as well: his girlfriend, his ex-wife, his doctor and other relatives. Many of them, the report explains, described Paddock as a narcissist, but "[b]y all accounts, Stephen Paddock was an unremarkable man whose movements leading up to Oct. 1 didn’t raise any suspicion," Lombardo said.

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The evidence shows that Paddock acted alone and was the only shooter. He had no ties to radical groups or ideology; his girlfriend told investigators that he was pleased when Donald Trump was elected president but did not appear to have any racial biases or discuss gun control. A primary care physician did tell investigators that Paddock may have been bipolar, and that he refused anti-depressants.

"An interview with his doctor indicated signs of a troubled mind," Lombardo explained, "but no troubling behavior that would trigger a call to law enforcement."

Additionally, investigators learned that Paddock's bank accounts dropped by about $1.5 million from September 2015 through September 2017. That loss of wealth "could have been a contributing factor," according to Lombardo.

"Without a manifesto, or even a note to answer questions, the totality of the information that has been gathered leaves us to only make an educated guess as to the motives of Stephen Paddock," he added.

Though investigators were unable to determine a motive for the Route 91 Harvest Festival shooting, they did find indication that Paddock had been planning such an event for quite some time. He purchased numerous firearms and was searching online for locations in the year leading up to the tragedy; he'd also rented hotel rooms next to the Lollapalooza festival in Chicago, Ill., and the Life Is Beautiful festival, also in Las Vegas.

Although the investigation has been closed, the FBI's Behavioral Analysis Unit is still working on a psychopathology report on Paddock. That report is expected to be released by the end of 2018.

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