The Las Vegas Police Department determined that there was no second gunman in the mass shooting at a music festival that killed 58 people last year—but authorities have been unable to determine shooter Stephen Paddock’s motive. Police have closed the 10-month investigation, and no one will face shooting charges. Authorities found that Paddock shot himself and was already dead when officers entered his hotel room the night of the massacre. Charges have been filed against the man who police said sold Paddock 720 rounds of tracer bullets. Clark County Sheriff Joe Lombardo called Paddock “an unremarkable man” with a troubled mind. Paddock committed the deadliest mass shooting in modern U.S. history when he fired into a crowd of 22,000 people at a country music festival from the Mandalay Bay Hotel’s 32nd floor.