Las Vegas gunman planned to escape - officials

The gunman behind the deadliest mass shooting in modern American history had planned to escape the scene, authorities say.

Retiree Stephen Paddock shot dead 58 concertgoers in Las Vegas on Sunday night, injuring a further 489 before taking his own life as police hunted him down.

Today Sheriff Joseph Lombardo said in a press conference there is evidence Paddock intended on escaping - but could not say what that evidence was.

The 64-year-old's car was found parked outside, with 1600 rounds of ammunition and several containers of an explosive commonly used in target shooting that totalled about 22kg inside.

Paddock had set up cameras in the hallway and hotel room - but none of them were recording. Police believe this was to make sure nobody was approaching his position as he fired rounds of ammunition into the crowd below.

"I believe because of his counter-measures placed in the people and placed in the hallway, he was in fear that he was about to be breached. So he was doing everything possible to figure out how he could escape," Mr Lombardo says.

The hotel room was rented to Paddock via Air BnB. He had also rented the downtown Las Vegas room at about the same time as an alternative music festival on September 22-24, where artists including Lorde, Chance the Rapper and Muse performed - but police do not know why.

Meanwhile, the FBI on Wednesday questioned Paddock's girlfriend, Marilou Danley, who says she had no idea he was "planning violence against anyone".

She returned late on Tuesday from a family visit to the Philippines.

Sheriff Lombardo says if Paddock did not feel his position was being breached, he could have continued firing. His hotel room contained 23 weapons, some of them modified to spray bullets, and thousands of rounds of ammunition.

"He could have continued firing... he had plenty of fire power available."

When officers used explosives to blast through into Paddocks hotel room, he was lying on the floor dead. It is unclear at what stage he took his own life.

In Thursday's press conference Mr Lombardo also commended the heroic actions of the hallway security guard. The shooter had sprayed 200 rounds of gunfire into the hallway as he approached his hotel room, but the guard was only hit in the leg.

"His bravery was amazing because he remained with our officers providing them with the key pass to access the rooms and he continued to help them clear rooms until our officer demanded he get medical attention."

Of the injured, 317 have been discharged already.