Child abuse images, snorkel equipment and handwritten notes were among the items found in the hotel room of Las Vegas shooter Stephen Paddock, police have revealed.

Following a three-month investigation, Las Vegas Police released a 81-age report on the mass shooting which killed 58 people and injured at least 500 more in October.

Paddock opened fire on a crowd of approximately 22,000 at country music festival on the Las Vegas Strip from the balcony of his 32nd-floor hotel room before killing himself.

When police broke in they found a stockpile of weapons – all of which had been bought legally – but, unlike other mass shooters, Paddock did not leave a manifesto or suicide note explaining his actions.

The preliminary report said police had found “several hundred images” of child pornography on a computer hard drive when they searched the four laptops belonging to Paddock, but officers are still investigating the source of the images.

Police also found notepads strewn around the room which had technical notes and reminders such as “unplug phones” and measurements including distance and bullet drop calculations.

Surveillance equipment and snorkel gear including a blue plastic tube with a snorkel mouthpiece, a scuba mask and a snorkel tube were also recovered from the room.

During a press conference, Clark County Sheriff Joe Lombardo said investigators had “gone over 2,000 leads and looked at 21,560 hours of video.”

Las Vegas shooting – in pictures Show all 15 1 /15 Las Vegas shooting – in pictures Las Vegas shooting – in pictures People scramble for shelter at the Route 91 Harvest country music festival after gun fire was heard Getty Las Vegas shooting – in pictures People carry a person at the Route 91 Harvest country music festival after shots were fired David Becker/Getty Las Vegas shooting – in pictures People run from the Route 91 Harvest country music festival after gun fire was heard David Becker/Getty Las Vegas shooting – in pictures A handout photo released via Twitter by Eiki Hrafnsson (@EirikurH) showing concertgoers running away from the scene (C) after shots range out at the Route 91 Harvest festival on Las Vegas Boulevard EPA/Eiki Hrafnsson Las Vegas shooting – in pictures People lie on the ground at the Route 91 Harvest country music festival after hearing gun fire Getty Las Vegas shooting – in pictures A man in a wheelchair is taken away from the Route 91 Harvest country music festival after hearing gun fire David Becker/Getty Las Vegas shooting – in pictures People stand on the street outside the Mandalay Bay hotel near the scene of the Route 91 Harvest festival on Las Vegas Boulevard EPA/Paul Buck Las Vegas shooting – in pictures FBI agents confer in front of the Tropicana hotel-casino after a mass shooting during a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures Las Vegas police run by a banner on the fence at the Route 91 Harvest country music festival grounds after shots were fired David Becker/Getty Las Vegas shooting – in pictures An injured person is tended to in the intersection of Tropicana Ave. and Las Vegas Boulevard after a mass shooting at a country music festival Ethan Miller/Getty Las Vegas shooting – in pictures Metro Police officers pass by the front of the Tropicana hotel-casino after a mass shooting at a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures A woman sits on a curb at the scene of a shooting outside of a music festival along the Las Vegas Strip AP/John Locher Las Vegas shooting – in pictures A cowboy hat lays in the street after shots were fired near a country music festival in Las Vegas Getty Las Vegas shooting – in pictures Las Vegas Metro Police and medical workers stage in the intersection of Tropicana Avenue and Las Vegas Boulevard South after a mass shooting at a music festival on the Las Vegas Strip Reuters/Las Vegas Sun/Steve Marcus Las Vegas shooting – in pictures Sheriff Joe Lombardo (2-R) speaking during a press briefing in the aftermath of the active shooter incident on Las Vegas Boulevard EPA

He said: “This report won’t answer every question, or even the biggest question as to why he did what he did.

“We are all going to have to be patient and let the investigation run its course.”

He added that all though they believed Paddock was a lone gunman, they are still investigating a person of interest in the case.

This is not Paddock’s girlfriend, Marilou Danley, who was previously a person of interest but has denied having any knowledge of his plans.

Sheriff Lombardo said it was unlikely that she would face criminal charges.

A total of 58 people were killed and more than 500 injured (Getty)

The report also tried to shed light on Paddock’s mental state in the weeks and months leading up to the shooting.

Weeks before the shooting, the couple stayed at Mandalay Bay hotel together but Paddock was acting strangely, Ms Danley told investigators.

She remembered him constantly looking out the windows overlooking an area where the concert would be held the next month.

He moved from window to window to see the site from different angles, the report said.

Paddock had become "distant" in the year before the shooting and their relationship was no longer intimate, Danley said during an interview with investigators. She described him as germophobic and said he had strong reactions to smells.

He had previously told friends and relatives that he always felt ill, in pain and fatigued.

His doctor thought he may have had bipolar disorder but told police that Paddock refused to discuss the possibility, the report said.

The doctor offered him antidepressants, but Paddock accepted only a prescription for anxiety medication. Paddock was fearful of medication and often refused to take it, the doctor told investigators.

The 64-year-old retired accountant and real estate investor had lost a "significant amount of wealth" since September 2015, which led to "bouts of depression," Sheriff Lombardo said.

Paddock had paid off his gambling debts before the shooting, according to the report.