The FBI has closed the investigation into the Las Vegas shooting without determining any motive by the shooter.

The mass shooting occurred during the Route 91 Harvest Festival on Oct. 1, 2017. The shooting left 58 dead and hundreds injured. Police were investigating the shooting for nearly 12 months.

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The FBI concluded there was no conspiracy or second shooter and were unable to determine a motivation for shooter Stephen Paddock. They did determine that Paddock has declining physical and mental health.

“It wasn’t about MGM, Mandalay Bay or a specific casino or venue,” Aaron Rouse, the agent in charge of the FBI’s Las Vegas office, told The Associated Press. “It was all about doing the maximum amount of damage and him obtaining some form of infamy.”

After shooting into the crowd, the 64-year-old fatally shot himself as police closed into his suite in a high-rise casino hotel. He did not leave any writing behind and was not seeking to further an agenda. The report says he was motivated by a combination of development issues, stress and struggles with interpersonal relationships.

Paddock was a retired postal worker, accountant and real estate investor who owned rental properties. He was a frequent gambler. He was also characterized by police as having no religious or political affiliations.

Also, the report states that Paddock’s “decision to murder people while they were being entertained was consistent with his personality.”

Police believe that he had planned to shoot himself after from the beginning. Police found 17 total guns at the scene and reported he started to collect the weapons about a year before the attack.

The shooting is the deadliest mass shooting in modern U.S. history.

More than 20,000 people attended the Las Vegas festival. The shooting took place as Jason Aldean headlined the festival near 10 p.m.