On Monday, Clark County Sheriff Joe Lombardo revised the chronology of the shooting and said the gunman, Stephen Paddock, had shot a hotel security guard through the door of his suite and strafed a hallway of the Mandalay Bay hotel and casino with 200 rounds six minutes before he unleashed a barrage of bullets into the crowd.

That account differed dramatically from the one police gave last week when they said Paddock ended his hail of fire on the crowd in order to shoot through his door and wound the unarmed guard, Jesus Campos.

"These people that were killed and injured deserve to have those six minutes to protect them," said Chad Pinkerton, an attorney for Paige Gasper, a California college student who was shot under the arm in the attack. "We lost those six minutes."

Maintenance worker Stephen Schuck told NBC News that he was checking out a report of a jammed fire door on the 32nd floor of Mandalay Bay when he heard gunshots and the hotel security guard who had been shot in the leg peeked out from an alcove and told him to take cover.