(CNN) The motive behind Stephen Paddock's slaughter of 58 people at Las Vegas' Route 91 Harvest music festival remains a mystery 10 months after the deadliest mass shooting in US history, according to a final criminal investigative report.

"The goal of our investigation all along has been to provide the public with the clearest picture possible of the events leading up to" the shooting last year, "as well as motive," Clark County Sheriff Joe Lombardo said Friday.

"What we have been able to answer are the questions of who, what, when, where, and how. What we have not been able to answer definitively is the why Stephen Paddock committed this act."

On October 1, the reclusive high-stakes gambler opened fire on the popular outdoor music festival from the 32nd floor of the Mandalay Bay Resort and Casino, killing 58 people and injuring hundreds. The festival was attended by about 22,000.

Lombardo on Friday released the 187-page, last criminal investigative report on the massacre from the Las Vegas Metropolitan Police Department.

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