Experts and law enforcement veterans caution that it can take time to establish a killers real motivations, piecing together electronic data with interviews and other shards of a life twisted into extreme violence.
Officials involved in the Las Vegas investigation have said they expect it will take an exhaustive search into Mr. Paddocks past, spanning multiple states and decades of his life, to deduce what brought him to the windows of the Mandalay Bay hotel with such an elaborate plan for murder. In F.B.I. speak, they want to understand his pathway to violence.
Andrew Bringuel, a former member of the F.B.I.s behavioral analysis unit, said investigators were undoubtedly exploring a range of motives that include personal, economic, social or political.
He could have been seeking revenge, said Mr. Bringuel, who retired earlier this year. This could have been a personal grievance. He could have been a sore loser. Gamblers like to talk about their winnings, but not their losses. I worked for the F.B.I. for a long time. The F.B.I. is pretty good at looking at the nooks and crannies of someones life. The bureau will end up with a hypothesis. Whether the bureau can prove it is a separate question.