By Sarah Young

DORKING, England (Reuters) - A man charged with trying to attack Donald Trump with a policeman's gun found it hard to cope with life but did not have political views and was never violent, his father told British media on Tuesday.

Michael Sandford was arrested after trying to grab a police officer's side arm at a Trump rally in Las Vegas on Saturday. When asked why, he told police: "To shoot and kill Trump," according to U.S. court papers.

"He's never shown any violent tendencies before. He's never been a bad person," his father, Paul Davey, was quoted as saying by the MailOnline website which put Sandford's age as 20. U.S. prosecutors have said he is 19.

"He's a nice kid and literally wouldn't hurt a fly - he used to tell us not to use fly spray because he didn't want any flies to die."

The Mirror newspaper's website quoted Davey as saying his son had Asperger's Syndrome and had left school at the age of 15 "because he couldn't cope with it all".

He went to the United States 18 months ago after an American girl he had met returned home, something that had made him "quite down and depressed," Davey said.

"He's been refusing to come back and we were worried about him, we were in contact with the American Embassy ... (but) the American authorities said 'he's over 18 we can't do anything.'"

Davey said someone must have coerced or "radicalised" his son into attacking the presidential candidate.

"He has never mentioned Donald Trump. The reason it is such a shock is because he shows no interest in anything like that ... I doubt he would even know who the president of the United States is."

Sandford lived on his own in Dorking, a commuter town near London, in a flat in a large white house.

A local who knew Sandford's mother, who did not want to be named, told Reuters Sandford had autism and obsessive-compulsive disorder.

"He was one of those guys who just stays in his room that's it, wouldn't come out," the man said.

The U.S. court documents said Sandford had been planning to kill Trump for about a year. He had visited a gun range the day before the rally to fire a weapon for the first time.

Last week, a British member of parliament was shot and stabbed to death in the street - an incident that has shocked a country that has strict gun controls and where attacks on public figures are rare.

Media reported that Sandford and his mother had taken part in a "Robot Wars" competition where contestants operate robots trying to destroy their opponents' machine.

A web page for the Fighting Robots Association listed Michael and Lynne Sandford and Paul Davey as owners of a number of robots, including machines named 'Mr Nasty', 'X-Terminator' and 'Steel Avenger'.

"He was quite active in the robot community for a while - buying famous robots from the show ... I then got them working for him because he had absolutely no idea about robots," John Findlay, director of the company behind Robot Wars, told the Mirror newspaper.

"He was calm, very quiet, a little bit weird and reserved."

(Writing by William James; Editing by Robin Pomeroy)