Criminal investigation

Gunman’s Vantage Point and Preparations Opened the Way for Mass Slaughter

From his hotel room on the 32nd floor of the Mandalay Bay Resort and Casino in Las Vegas, Stephen Paddock would have looked down upon a crowd of more than 20,000 people, surging to the final sets of a country music festival.

He opened fire late Sunday, killing at least 59 people and injuring 527 others in one of the deadliest mass shootings in American history, the authorities said.

But what may have seemed like a difficult feat, firing across an urban area and into a crowd from about 500 yards away — the equivalent of several football fields — appears to have been offset by Mr. Paddock’s preparations, which made it possible for him to inflict mass carnage.