Jan. 29 (UPI) -- The FBI announced Tuesday it could find no motive for the October 2017 shooting in Las Vegas that left 58 people dead and hundreds injured.
The bureau's Las Vegas Review Panel released a three-page report, saying Stephen Paddock, who died of a self-inflicted gunshot wound, exhibited "no single or clear motivating factor" for the mass shooting. The conclusion comes 15 months after the shooting at a country music festival outside the Mandalay Bay Resort and Casino.
"The LVRP concludes that Paddock's attack was neither directed, inspired nor enabled by ideologically motivated persons or groups," the report said. "Paddock was not seeking to further any religious, social or political agenda through his actions."
The FBI said Paddock acted alone when he opened fire from the 32nd floor hotel room at Mandalay Bay. The report said it's rare for a shooter such as Paddock to have a singular motive for such an attack.
"Throughout his life, Paddock went to great lengths to keep his thoughts private, and that extended to his final thinking about this mass murder," the report said.
"More often their motives are a complex merging of developmental issues, interpersonal relationships, clinical issues and contextual stressors."
One day after the shooting, Paddock's brother, Eric Paddock, said he was "completely dumbfounded" his brother would engage in such an act of violence.
"There is no reason we can imagine why Stephen would do something like this," he said.
Paddock lived in a retirement community in Mesquite, Nev., with his girlfriend Marylou Danley. Although he was known to local police, he had no conflicts with law enforcement.
An autopsy revealed no further insights into Paddock's motivation, though the presence of certain chemicals in his urine indicated he may have taken the anti-anxiety medication Valium, the coroner's office said in February..
The FBI said that in the years before the attack, Paddock had complained about his declining physical and mental health, leading him to plan the attack with suicide in mind.
"His inability or unwillingness to perceive any alternatives to this ending influenced his decision to attack," the report said. "The planning and preparation -- in and of itself -- was likely satisfying to Paddock as it provided a sense of direction and control despite his mental and physical decline."
He desired to achieve a degree of "infamy" through a mass casualty attack, the bureau concluded.
The Bureau of Alcohol, Tobacco and Firearms, meanwhile, said the shooter purchased 33 of the 50 firearms he owned in the year prior to the shooting, most of them rifles.
Clark County Sheriff Joe Lombardo described the shooting as "obviously premeditated." Police recovered 23 guns and an assortment of cameras from his hotel room. At least one camera was trained on the hotel hallway, presumably to observe police approaching his door.