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According to BBC, the former offshore worker William Kelly, even shouted "die, die" as Cathy Kelly was engulfed in flames.
A jury heard his only concern after the blaze last February was the safety of his West Highland terrier, Poppy.
A judge described his actions in the home they shared in Kilmaurs Road, Kilmarnock as "horrific".
Jailing Kelly for life, judge Lady Stacey said: "I understand you maintain your denial of the crime and have shown no remorse.
"I also note from having heard the evidence that you said a few weeks after your mother's death you did what you had to and she deserved what she got.
"The jury found you guilty of murdering your mother, you assaulted her by pushing her and putting her to the floor before you poured petrol on her and set her alight - that is a horrific crime."
Throughout his trial Kelly denied murdering his mother on 11 February last year.
He said he had never hit her and claimed she had been set on fire by accident after he cleaned a car part in the garage and spilt petrol on his trousers and trainers.
Kelly claimed that as he bent over his mother as she lay on the living room floor he lit a cigarette and there was a blue flash.
But the court heard that Kelly was angry because his mother had embarrassed him at a 21st birthday party by drinking too much.
He ordered his mother and his then partner Eleanor Banks to leave and called a taxi.
When they returned home at about 23:00 he dragged his mother by the arms into the house after she fell as she got out the taxi.
Kelly then punched and kicked the OAP on the head and body in the living room of their home.
Ms Banks, 44, told prosecutor Ashley Edwards QC: "William was emptying a petrol can onto his mum - all over her - and I couldn't stop him.
"I was standing screaming 'You're going to kill your mum' and he was saying 'die'.
"He went down and he set fire at the bottom of her legs.
"She just went up like an inferno. I've never seen anything like it."
A pathologist said Ms Kelly suffered bruising, broken ribs and second degree burns to 45% of her body.
Jurors heard that she was recovering from a brain haemorrhage, which she suffered in December 2016, and it was alleged that this was caused by beatings inflicted by violent Kelly.
Heartless Kelly even boasted in a text of wanting to give his mother "two black eyes for Christmas."
When the killer was being treated for burns he confessed to a nurse who was treating him and told her: "I did what I had to do.
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