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.”

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.

It seems clear that Paddock knew what he planned to do weeks ahead of time, sending his girlfriend to visit family in the Philippines and subsequently wiring her large sums of money (around $150,000) prior to the attack. Marilou Danley, Paddock’s girlfriend, returned to the United States after the attack, relaying to authorities that her boyfriend had regularly espoused the idea that her Christian God “didn’t love” him.

Ultimately, Paddock would take his own life before law enforcement used explosives to blow down the door to his suite, where they’d find over a thousand spent shell casings littering the floor around the 64-year-old man’s body and a collection of 23 firearms. Some were equipped with “bump stocks,” which allow the user to fire a semi-automatic weapon at a rate resembling that of a fully-automatic firearm. Paddock’s use of bump stocks would lead to bi-partisan political support for a ban of such modifications in the United States–a ban that has proven unpopular among some segments of President Trump’s conservative base.

Paddock had lamented the federal government’s response to Hurricane Katrina and had posted social media rants about law enforcement standoffs with people in Waco, Texas in 1993 and Ruby Ridge, Idaho in 1992. It prompted some to draw parallels between Paddock and domestic terrorists like Timothy McVeigh, but Paddock had no known affiliations with religious, political, or extremist groups. He began stockpiling weapons and accessories more than a year before the attack, while simultaneously beginning to distance himself from his girlfriend and friends–pointing to a plan that was developing in his head for some time.

Police found no suicide note, no long-winded video diatribe, no killer manifesto like you might expect from one of the most devastating acts of domestic terrorism in U.S. history, placing its characterization as a “terror attack” in question–as terrorism is traditionally seen as a means to try to force political change.

Paddock may not have been a terrorist at all. He may have just been a deranged man with a well-funded bank account. Unfortunately, we may never know.