The FBI ended its investigation into the 2017 mass shooting in Las Vegas without concluding the gunman’s motive.

Aaron Rouse, the special agent in charge of the FBI’s Las Vegas office, told the Associated Press the exact motive behind Stephen Paddock’s attack on Oct. 1, 2017 was still unknown after months of examination by agents and behavioral specialists.

“It wasn’t about MGM, Mandalay Bay or a specific casino or venue,” Rouse said. “It was all about doing the maximum amount of damage and him obtaining some form of infamy.”

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He added that Paddock was a 64-year-old retired postal service worker who was known to engage in high stakes gambling. His younger brother once called him the “king of microaggression” and suggested he may have sought fame through the attack, according to the AP. Police characterized him as a loner.

His girlfriend informed authorities Paddock had said doctors told him he had a “chemical imbalance.” A Reno car salesman also told police that in the months leading up to the shooting Paddock told him he was depressed and had relationship troubles, according to the AP.

Local police in August concluded their investigation and also were not able to determine a motive for the attack that killed 58 people at a concert and inured almost 900. The attack ended when Paddock fatally shot himself.

Paddock fired from his room on the 32nd floor of the Mandalay Bay Resort and Casino into a crowd of concert-goers, using an array of assault rifles, many of which were fitted with bump stocks. Authorities said the weapons were bought legally.