Graeme Morris attacked parents Anne, 63, and Fred, 64, after turning up unexpectedly at the couple's £400,000 bungalow in Troon, Ayrshire, in October last year.
Morris – an unemployed artist – flew into a rage after mistakenly believing his parents had harmed him as a child.
Mrs Morris died from a serious heart condition that had been diagnosed in 1996.
Morris yesterday admitted to the culpable homicide of his mother when he appeared at the High Court in Glasgow. The 38-year-old, who has a previous conviction for violence, also pled guilty to assaulting his father to the danger of his life.
The court heard that Morris's last partner, Emma Russell, had become concerned about his behaviour in the year prior to the killing.
Former Glasgow School of Art student Morris, described as strange and eccentric, was said to be obsessed with the idea that he was a genius. He also made false allegations he had previously been harmed by his parents.
Miss Russell found him a GP and it appears he was put on a waiting list to see a psychiatrist.
However, on October 5 last year – the day of the attacks – Morris travelled from his home in Brighton to his parents' house in Troon.
The couple were sitting in the conservatory and his mother seemed shocked to see him. Morris said: "I'm here to see you and him. If you still deny it, you must be part of it, you f****** bitch."
He grabbed his mother by the hair and threw her on to a sofa before punching his father to the floor. As Mrs Morris tried to get up, her son slapped her face.
Morris then continued battering his father as he lay on the ground. He then went out into the garden appearing to look for a spade.
Prosecutor Andrew Miller told the court: "He explained to police he planned to scare his father into believing he was going to dig a hole for him."
Mr Morris fled his property in Polo Gardens and went to a nearby house for help. The court heard Morris stormed after his father and dragged him across the ground.
Mr Miller said: "The accused continued his assault and then stripped his father naked apart from his socks before repeatedly kicking him."
Morris made his escape shortly before police arrived. He initially went to Troon beach to change his clothes before boarding a train to Glasgow.
Police, meanwhile, discovered a badly beaten Mr Morris, who told him his son was responsible.
Mrs Morris was then found slumped on a sofa apparently not breathing. The couple were both taken to hospital but Mrs Morris was pronounced dead.
The court heard that the next morning Morris called Miss Russell before he boarded a train to London. He told her he had "hit his dad" adding: "I think my mum is dead – I think she's had a stroke or a heart attack. I don't know if I am sane or insane or should be locked up in a loony bin."
Morris was detained as he got off the train at Euston Station before being brought back to Scotland for questioning.
He confessed to hitting his parents. Morris added: "I didn't murder my mother. I didn't have any intention of murdering either of my parents or killing them or for them to die."
Morris's QC, Mark Stewart, said it was clear the attacks were "borne out of the mental illness" the killer was suffering at the time.
Judge Lord Uist imposed an interim compulsion order for Morris to remain at the State Hospital in Carstairs.
Morris will return to the dock in May.
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