COPS probing the Las Vegas concert massacre have found a mystery charger in Stephen Paddock's hotel room that doesn't match any of his phones.

The discovery has prompted detectives to question whether anyone else stayed with Paddock in the Mandalay Bay hotel in the days before the slaughter.

14 Stephen Paddock killed 58 people in a nine-minute shooting spree Credit: AP:Associated Press

Paddock killed at least 58 and injured more than 500 others after he sprayed bullets from his room on the 32nd floor on Sunday night.

The millionaire property developer, 64, was found dead by cops with a reported self-inflicted gunshot wound after the massacre.

His phones and other devices are under examination.

Garage records also reportedly show when Paddock’s car drove away from the hotel, one of his key cards was used to get into the room.

It has also emerged that the night before the massacre, Paddock contacted hotel security to complain about another guest’s country music.

CBS News reports that he actually called them twice about this.

Cops also believe Paddock had been plotting an escape route after finding he had lined the inside and outside of his room with surveillance cameras to spot officers approaching.

But five days after the deadliest mass shooting in recent US history, authorities acknowledged today they have not uncovered a "clear motive" for the gunman.

"We still do not have a clear motive or reason why," Undersheriff Kevin McMahill of the Las Vegas Metropolitan Police Department told reporters.

"At this time I'll tell you we have no credible information to report to you as to motivation."

Adding to the mystery was the discovery of a cryptic note full of random numbers.

The piece of paper was found near his dead body and Sheriff Lombardo said it’s been sent off for analysis.

It is not believed to be a suicide note.

14 Workers board up a broken window at the Mandalay Bay hotel, where shooter Stephen Paddock conducted his mass shooting Credit: Reuters

14 Inside the hotel room where police are hunting for clues about the killers' motive

Stephen Paddock killed 58 people and left hundreds injured in Las Vegas after raining bullets on a crowd at an open-air country music concert while perched in a 32nd floor hotel room.

Authorities found 1,600 rounds of ammunition and 50 pounds of explosives in the former millionaire and prolific gambler's car.

It has now emerged the 64-year-old booked rooms overlooking the Lollapalooza festival in Chicago in August and the Life Is Beautiful event near the Vegas strip just weeks ago.

Authorities also announced a Hyundai Tucson had been found in a search of his home in Reno, Nevada, which they had been searching for as part of the probe.

14 Veronica Hartfield, widow of slain police officer Charleston Hartfield, with their son Ayzayah, 15, and daughter Savannah, 9, at a vigil Credit: Getty Images - Getty

14 Colleagues of the fallen officer held candles in tribute Credit: Getty Images - Getty

14 Armed forces personnel also attended the emotional service Credit: Getty Images - Getty

Police are also probing whether he may have been planning further attacks - including a car bomb.

And they have confirmed a note found by Paddock's body was not a suicide note and they are not yet certain whether the gunman meant to take his own life.

Author and online commentator Thomas Wictor speculated Paddock's body position suggests he may have accidentally shot himself while collecting weapons and moving through the hotel room after hearing someone approaching the door.

Police do not yet know at what stage Paddock died.

Meanwhile, thousands attended emotional vigil was held for fallen off-duty Las Vegas police officer Chaleston Hartfield last night, including his 15-year-old son and nine-year-old daughter.

It is the latest in a series of public events to honour the dead as America comes to terms with the worst mass shooting in its history.

14 Paddock's girlfriend Marilou Danley was flown back to the US on Tuesday

14 She has said she will fully co-operate with the FBI investigation Credit: AFP or licensors

Investigators have been interviewing Paddock's girlfriend Marilou Danley after she was flown back from the Philippines on Tuesday night and the FBI hopes she will hold the key in finding out why the massacre took place.

Paddock bought Danley tickets to return to her native Philippines before the killing and also transferred her money to buy a house in her homeland.

Danley said she thought he gave her the money as a way of breaking up with her.

Officials have said they find it "hard to believe" Paddock could have devised the plot without help - and that he also had a plan to escape the area alive.

The former millionaire and prolific gambler shot himself inside his Mandalay Bay hotel room when it was stormed by a SWAT team at around 11pm on Sunday (7am Monday UK time).

Clark County Sheriff Joseph Lombardo: "You have to make an assumption that he had some help at some point.

"What we know is that Stephen Paddock is a man who spent decades acquiring weapons and ammo and living a secret life, much of which will never be fully understood.

14 Danley told the FBI she believes Stephen Paddock was suffering mental health problems before the massacre Credit: Twitter

14 An arsenal of guns were found inside the killer's hotel room in Las Vegas

14 Cops found 23 firearms in Paddock's Mandalay Bay hotel suite

"Maybe he's a super guy. You know, a super yay-hoo that was working out all this on his own. But it would be hard for me to believe that."

Lombardo said Paddock had been "meticulously" building up weapons and planning the shooting and is "troubled" the mass killer was able to move his huge arsenal of weapons into the hotel room.

He added Paddock had 1,600 rounds of ammunition and several containers of an explosive commonly used in target shooting in his car.

Lombardo refused to say what led authorities to believe he planned to flee the scene but it is known Paddock lined his room and the corridor with cameras so he could see police approaching.

Police are now investigating what happened in the hour between the last gunshot being fired and Paddock being found dead in his hotel room.

The gunman was shooting for around nine minutes amid scenes of mass panic as officers tried to find the killer.

14 Paddock's body lies surrounded by guns and bullet casings in the hotel room

14 People light candles during a memorial for victims of the shooting Credit: Reuters

14 People gather at a makeshift memorial in the middle of Las Vegas Boulevard Credit: Reuters

In a statement released yesterday, Danley said: "I knew Stephen Paddock as a kind, caring, quiet man.

"I loved him and hoped for a quiet future together with him. He never said anything to me, or took any action that I was aware of, that I understood in any way to be a warning that something horrible like this was going to happen.

"A little more than two weeks ago, Stephen said he found a cheap ticket for me to the Philippines and that he wanted me to take a trip to see my family.

"Like all Filipinos abroad, I was excited to go home and see family and friends.

"While there he wired me money which he said was for me to buy a house for me and my family.

"I was grateful, but honestly I was worried that first the unexpected trip home and then the money was a way of breaking up with me.

"It never occurred to me in any way whatsoever that he was planning violence against anyone.

"I have not made a statement until now because I have been co-operating with authorities and I voluntarily flew back to America because I know the FBI and Las Vegas Police Department want to talk with me and I want to talk with them.

"I will co-operate fully with them. Anything I can do to help ease suffering, I will do."

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