Three members of the same family died following a bungalow fire, believed to have been started by the father who had a history of mental illness, a court has heard.
Ten-year-old Ben Philpotts was thought to have been bludgeoned with a sledgehammer as he lay in his bed around 6am on January 18, 2010. His mother, Patricia Philpotts, died almost instantly in a blaze which was believed to have been started in her bedroom around the same time Ben was attacked, while Harold Philpotts fled from the property.
Ben was pronounced dead that morning, while Mr Philpotts died in hospital eight days later, suffering from multiple organ failure.
A police investigation subsequently suggested that 47-year-old Mr Philpotts had been responsible for the deaths of his young son and estranged wife, at the property in Trevarrian, Newquay, Cornwall.
At an inquest into their deaths today, a statement was read from Mrs Philpotts' mother, Betty Bantock, in which she described her son-in-law as a "Jekyll and Hyde character", who had a history of hypochondria including being convinced he had HIV and cancer.
On one occasion, he demanded doctors also test his son for HIV, having been convinced - wrongly - the pair were infected.
The hearing in Truro was told Mr Philpotts, also known as Harry, was a regular visitor to the bungalow at weekends, and was unhappy about the prospect of having to return to his flat on the morning of the incident - his 47th birthday.
Mrs Bantock told police: "I can only assume that Pat had a few words with Harry to go back to his flat. He never wanted to go back."
She said she woke up around 6am on the day of the fire, sharing a cigarette with her daughter - a data entry clerk at Royal Cornwall Hospital, Treliske - in their conservatory, before Mrs Philpotts went upstairs to her room.
Earlier, Mr Philpotts had been seen "pacing up and down" the conservatory while also having a cigarette. He returned inside the main part of the property when the others went out to smoke, she said.
"I then heard a terrific explosion," she said in a statement.
"It was like a bomb going off, and then shattering of glass.
"That's when Harry came back downstairs."
Mrs Bantock's granddaughter - Mrs Philpott's niece, who also lived, downstairs, in the property - said she heard screams from upstairs, as Mr Philpotts walked down the stairs towards the kitchen.
Mrs Bantock, 80, said: "He walked straight past me.
"I was still stood in the kitchen and I turned my head to look at him.
"He didn't say anything to me.
"I thought he was going for a cigarette.
"I didn't see any burns."
Emergency services were called but could not save 44-year-old Mrs Philpotts or her son.
The court heard there were two petrol cans found in Mrs Philpotts' room where the fire is believed to have started, while a sledgehammer weighing 7.4kg was found in Ben's bed.