Las Vegas mass shooter Stephen Paddock meticulously planned and carried out his attack in a sick bid to become infamous, a new FBI report reveals.

Paddock, 64, slaughtered 58 people when he rained bullets down on an outdoor country music festival in the Nevada, US, city in October 2017.

Acting alone, the gunman fired more than 1,000 rounds over an 11-minute period from the 32nd floor of the Mandalay Bay Resort and Casino.

After killing dozens and injuring hundreds of others, he then shot himself dead as police assembled in the hallway outside his hotel room.

This week, the FBI released a three-page report following a year-long investigation into the deadliest mass shooting in modern US history.

The document describes how Paddock, armed to the teeth with high-powered rifles, had taken "multiple, calculated" steps ahead of the attack.

Stephen Paddock, 64, slaughtered 58 people when he rained bullets down on an outdoor country music festival
The armed gunman shot himself dead as police assembled in the hallway outside his hotel room

It also reveals he had wanted to attain a degree of infamy through a mass-casualty atrocity - and was influenced by the memory of his criminal dad.

But despite wanting to do "the maximum amount of damage", there was found to be no clear motive for his massacre on October 1, 2017.

More than 800 people were injured in the horrific rampage, which took place at the Route 91 Harvest music festival on the Las Vegas Strip.

Among the deceased victims was a husband who died shielding his wife.

According to the agency's report, Paddock was no different from many other mass shooters driven by a complex mix of issues, ranging from mental health to stress, who wished to die by suicide.

He was not found to be motivated by any ideological or political beliefs.

Paddock was caught on camera bringing 21 suitcases full of guns into the hotel before the massacre (
Image:
New York Times)
Police found a stockpile of weaponry when they stormed his room (
Image:
LVMPD)

"There was no single or clear motivating factor behind Paddock's attack," the FBI's Behavioral Analysis Unit said, echoing a report issued by Las Vegas police in August last year.

The gunman had displayed minimal empathy throughout his life.

And his decision to murder people while they were being entertained was consistent with his personality, according to the report.

As was his nature, he carefully planned the attack, amassing an arsenal of guns and ammunition during a year-long shopping spree.

He also methodically researched police tactics and site selection.

That work provided a "sense of direction" for him as he suffered a decline in his physical and mental health, the document says.

People run from the Route 91 Harvest music festival after Paddock opened fire (
Image:
Getty Images North America)
The shooter had displayed minimal empathy throughout his life (
Image:
AFP)

“The planning and preparation — in and of itself — was likely satisfying to Paddock as it provided a sense of direction and control despite his mental and physical decline," it states.

Chillingly, the killer had no plan to escape the Mandalay Bay alive.

"Paddock took multiple, calculated steps to ensure that he could commit suicide at a time and in a manner of his choosing," the report said.

It added that the shooter used surveillance cameras in the attack, and brought one handgun to the room that he used to shoot himself. 

He left no suicide note or explanation about the attack.

"Throughout his life, Paddock went to great lengths to keep his thoughts private, and that extended to his final thinking about this mass murder," officials said in the report.

Paddock opened fire from the 32nd floor of the Mandalay Bay Resort and Casino (
Image:
AFP)
People hug and cry outside the Thomas & Mack Center following the massacre (
Image:
Getty Images North America)

An important aspect of the attack was Paddock's desire to die by suicide amid his decline in health and financial status, according to the document.

He "concluded that he would seek to control the ending of his life via a suicidal act", it states.

The report portrays Paddock as having been heavily influenced by his bank robber dad, who was once on the FBI's 'most wanted' list.

The gunman is said to have viewed others in a similar way to his approach to gambling - each life was transactional, the New York Times reports.

Agent Aaron Rouse, of the FBI’s Las Vegas office, said the mass shooting was "all about" Paddock doing "the maximum amount of damage".

He added that the shooter also wanted to gain infamy.