FILE - This undated file photo provided by Eric Paddock shows his brother, Las Vegas gunman Stephen Paddock. Police initially said Stephen Paddock stopped firing on the music festival concert crowd below to shoot through his door and wound a Mandalay Bay security guard who was outside. On Monday, Oct. 9, 2017, they said the guard actually was wounded before Paddock started the massacre. (Courtesy of Eric Paddock via AP, File)
FILE - This undated file photo provided by Eric Paddock shows his brother, Las Vegas gunman Stephen Paddock. Police initially said Stephen Paddock stopped firing on the music festival concert crowd below to shoot through his door and wound a Mandalay Bay security guard who was outside. On Monday, Oct. 9, 2017, they said the guard actually was wounded before Paddock started the massacre. (Courtesy of Eric Paddock via AP, File)

Mandalay Bay hotel officials didn’t notify police about a shooting in a hallway inside the high-rise until after Stephen Paddock opened fire on the crowd at a country music festival outside, a federal official told The Associated Press on Thursday.

The disclosure means there may have been a delay of some six minutes in summoning police to the scene of what became the deadliest mass shooting in modern U.S. history. The official was briefed by law enforcement but wasn’t authorized to discuss the matter publicly and spoke on condition of anonymity.

In the most recent chronology given by investigators, Paddock sprayed 200 rounds into the hallway on the 32nd floor Oct. 1, wounding an unarmed security guard in the leg, six minutes before he unleashed his barrage of bullets on the festival crowd. He killed 58 people and injured nearly 500. Over the past few days, Las Vegas police and the Mandalay Bay’s corporate parent, MGM Resorts International, would not answer questions about when the hotel notified police.