Las Vegas police have released new details on the "hero" Mandalay Bay security guard who helped stop the gunman who killed 58 people and injured hundreds of concertgoers on Oct. 1.

"Jesus Campos is a true hero," Undersheriff Kevin McMahill said in a news conference Friday. "We now know that he was dispatched to a door alarm on the 32nd floor. He went up there to investigate the open door, and as he was doing his job, he came under fire by our suspect."

Campos was struck in the leg, retreated and notified his dispatcher, McMahill said. "This was a remarkable effort by a brave and remarkable man," he said.

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"I don't think we've done enough in recognizing [Campos] and his actions, and today, I want to apologize, and clear the record that he's an absolute hero," McMahill said.

Paddock fired well over 200 rounds into the hotel hallway but Campos was only struck in the leg, Clark County Sheriff Joseph Lombardo said Thursday. "It's amazing that [Campos] didn't sustain an additional injury," he said.

Lombardo said that Campos' bravery was "amazing" because he remained with officers, provided them with the key to enter the hotel room, and "continued to help [officers] clear rooms until our officer demanded that he go seek medical attention."

David L. Hickey, the union president representing the hotel's security officers, told The New York Times that Paddock did not resume firing on concertgoers after focusing his attention on Campos.

In another development in the investigation, CBS News justice and homeland security correspondent Jeff Pegues reports that the gunman's vehicle may have been primed to explode.

Law enforcement sources say there were at least 1,000 rounds of ammunition in a suitcase and Tannerite in a duffle bag inside the vehicle in a parking garage. Tannerite, used in target shooting, explodes when hit by rifle fire.

Could Paddock have been planning to shoot at it? Could he have used it as an explosive if fired upon by police while trying to escape? These are some of the questions investigators are considering as they try to determine a motive for the mass shooting, Pegues reports.