The Las Vegas gunman lost tens of thousands gambling weeks before the massacre, new FBI documents reveal

The high-roller gambler, who opened fire on concert-goers on the Las Vegas Strip in 2017, had lost tens of thousands of dollars gambling weeks before the mass shooting and was upset at how casinos had treated him, according to newly released FBI documents.

The documents reveal the strongest clue to a motive for the deadliest mass shooting in modern US history.

They draw a detailed account of gunman Stephen Paddock’s final days before the October 1, 2017 mass shooting that killed 60 and injured hundreds more.

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One player, whose name has been redacted from the hundreds of pages of documents, told the FBI that Paddock was “very upset at how the casinos were treating him and other high rollers.”

Neither the FBI nor the Las Vegas Metropolitan Police Department, the lead investigative agency, gave an official motive for the shooting.

Both agencies said Paddock acted alone.

The 10-minute massacre occurred on the final night of the three-day Route 91 Harvest music festival across from Mandalay Bay Resort.

Authorities said Paddock, 64, had moved out of his corner suite on the 32nd floor.