Las Vegas: Police have dramatically changed their account of how the Las Vegas massacre began on October 1, revealing on Monday that the gunman shot a hotel security guard six minutes before opening fire on a country music concert. The change raises new questions about why police weren't able to pinpoint the gunman's location sooner.

Officials had previously said that gunman Stephen Paddock, 64, of Mesquite, Nevada, shot Mandalay Bay security guard Jesus Campos after Paddock had unleashed his deadly volley at the Route 91 Harvest country music festival, an assault that began at 10.05 pm.

Heal said that if police had known immediately that a guard had been shot, they would have rushed the room while the gunman was still firing. He said it seemed to signal a breakdown in communication.

"It doesn't say much for hotel security," Heal said.

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After Campos was shot, a maintenance worker appeared on the 32nd floor and "Campos prevented him from receiving any injuries," Lombardo said.

Representatives for the Mandalay Bay hotel casino and the union representing Mandalay Bay's security guards did not immediately respond to messages seeking comment.

Lombardo said investigators still had not uncovered a motive for Paddock's attack and had found "zero" evidence of a second gunman.