More than a year ago, Stephen Paddock, a retired postal worker who liked to do his gambling in increments of $10,000 or more, opened fire on an unsuspecting crowd from his vantage point high above in a suite Mandalay Bay had provided to him free of charge.

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

FBI closes investigation into Las Vegas shooting, but the motive remains a mystery
A window is broken on the 32nd floor of the Mandalay Bay Resort and Casino where a gunman opened fire on a concert crowd on Sunday night, October 3, 2017 in Las Vegas, Nevada. (Photo by Drew Angerer/Getty Images)

Unfortunately, after interviewing countless witnesses and exploring every facet of Paddock’s life leading up to what would become the most deadly mass shooting in American history, the FBI could offer no further insight into what prompted the attack. In fact, the shooter’s motive may never be known–assuming he had one worthy of discussion.

The FBI has concluded that Paddock worked alone as he prepared and executed his plan. They also know that he had sought medical care for depression, but that he refused a prescription that could help, telling friends instead that he was sick with a “chemical imbalance” that doctors said they could not cure. A self-made and self-reliant man, Paddock grew up the child of an infamous bank robber, raised largely by a single mother who struggled to provide a financially-stable home. As an adult, Paddock’s brother characterized him as the “king of microaggression,” stating plainly that his brother was narcissistic and detail-oriented enough to plan such a terrible attack.