A British man arrested at a Donald Trump rally in Las Vegas told authorities he tried to grab a police officer's gun and wanted to shoot the billionaire Republican presidential candidate.

Protester Michael Steven Sandford, who appeared in court on Monday, even went to a gun range on Friday so he could learn how to fire a pistol.

The 20-year-old was arrested at the Treasure Island Hotel and Casino on Saturday after going for a metro police officer's gun.

Sandford, who is originally from Surrey and was carrying a UK driver's licence, had been living illegally for 18 months in New Jersey after his visa expired and had been sleeping in his car.

A secret service report said Sandford told officers he had been planning the Vegas assassination for around 12 months and believed he would die in the process.

He also had tickets for a rally in Phoenix later that day in case the gun grab failed and told officers if Trump 'were on the street tomorrow, he would try this again'.

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Arrest: Michael Steven Sandford was taken out of the Trump campaign rally at the Treasure Island Hotel and Casino in Las Vegas on Saturday, pictured, after allegedly trying to disarm a police officer with the intention of killing Trump

Plot: Michael Steven Sandford, 20, even went to a gun range on Friday so he could learn how to shoot. He is pictured being removed from the rally

Held: Sandford was arrested after allegedly grabbing the handle of an officer's gun in an attempt to remove it

Bereft: Police escort Michael Sandford's mother from her flat in Dorking today after her son's arrest

The court heard from a public defender that Sandford is autistic, while his mother Lynne told federal magistrate judge George Foley in a statement that he had been treated for obsessive compulsive disorder and anorexia when younger.

Despite living in Hoboken for 18 months, he did not have permission to be in the US and was unemployed and living out of his car.

Sandford was charged with an act of violence on restricted grounds, according to a complaint filed on Monday in US District Court in Nevada.

It cites a report by Special Agent Swierkowski, whose first name was not included, saying Sandford told officers he drove from California to kill Trump and went to a Las Vegas gun range the day before to learn to shoot.

Sandford later went to a Trump rally at Treasure Island and approached a Las Vegas police officer to say he wanted an autograph from Trump.

The report says Sandford was arrested after grabbing the handle of an officer's gun in an attempt to remove it. He was filmed by local station KLAS being led away.

According to the complaint, Sandford had targeted officer Ameel Jacob's weapon because it was in an unlocked position and would be the easiest way to acquire a gun to shoot Trump.

Court papers read: 'Sandford further stated that if he were on the street tomorrow, he would try this again.

'Sandford claimed he had been planning to attempt to kill Trump for about a year but decided to act on this occasion because he finally felt confident to do it.'

The British national had lived in Hoboken, New Jersey, for around 18 months and had driven to San Bernardino in California before heading to Las Vegas on Thursday.

In daTrump spoke to a crowd at the Treasure Island hotel and casino, seemingly oblivious to the drama that was unfolding in the audience

Speech: Donald Trump speaks at a campaign rally in a packed 1,600-seat theater at the Treasure Island Hotel and Casino where he declared the Orlando massacre demonstrated the need to fight terrorism

His mother, Lynne Sandford, 41, was today taken away from her home in Dorking, Surrey, by police.

A neighbour, who asked not to be named, saw the events unfold. He told MailOnline: 'I am not sure what was going on but the police came here this morning and they took away Lynne and a slightly older lady, but I don't know who she was.'

Evidence: The suspect's mother Lynne told federal officers that her son had been treated for obsessive compulsive disorder and anorexia

Michael Sandford had been living out in the States for nearly two years before he was arrested.

He used to live less than a mile from his mother's flat in Dorking, but moved across the Atlantic to New Jersey.

A woman who lives in his former flat said: 'I never met him but he used to live in our flat. We still get his mail from time to time.'

The three-storey cream coloured building used to be allocated to people who suffered from mental health issues but did not need permanent care. However, a neighbour said that the flats had since been sold on to a private landlord who rents them out to new tenants.

Another neighbour added: 'I recognised his face from the pictures but I don't know him. I have definitely seen him around here before. He must have had really strong political views to try to do that.'

He told police he visited the Battlefield Vegas shooting range on Friday where he fired off 20 rounds from a 9mm Glock pistol to learn how to use it.

Sandford also told investigators he had a ticket for a Trump rally in Phoenix, Arizona, for later on Saturday as a back-up.

Authorities said on Saturday that law enforcement officers were able to take Sanford into custody with little disruption.

The judge declined to grant bail to Sandford, pending a further hearing, saying the accused was a risk to the community and a flight risk.

The Trump campaign directed questions to U.S. Secret Service, which did not immediately respond to a request for comment.

A spokesman for Britain's Foreign Office said: 'We are providing assistance following an arrest of a British national in Las Vegas.'