Clark County Sheriff Joe Lombardo says investigators still have not figured out why the Las Vegas shooter decided to open fire on a concert crowd that killed at least 58 people.

Lombardo also says they have not found any evidence of a second shooter or any connection to terrorist groups.

However, some of the timeline has changed.

The sheriff now says Stephen Paddock shot at a casino security guard before turning to the crowd.

The guard told investigators that Paddock was drilling into an adjacent wall when he walked up to the room at the Mandalay Bay Hotel and Casino.

"There was drilling done. It was to the doorway adjacent wall to the doorway. And just an assumption would be to either place a camera or to place a rifle, but the drilling was not completed," Lombardo said.

Lombardo says Paddock tried to create a diversion by firing at fuel tanks.

He planned the massacre so meticulously that he even set up cameras inside the peephole of his high-rise hotel room and on a service cart outside his door, apparently to spot anyone coming for him, authorities said.

Investigators also found a computer and 23 guns with him at the hotel, along with 12 “bump stock” devices that can enable a rifle to fire continuously, like an automatic weapon, authorities said. Nineteen more guns were found at Paddock’s Mesquite home and seven at his Reno house.

Investigators are still speaking with the shooter's brother who lives in Orlando and girlfriend to get more information.