A thug caught on camera murdering his step-father has been jailed for at least 17 years.
Dean Martin carried out a horror hammer attack on Keith Allan hitting the 42 year-old at least 15 times.
Two children cowered upstairs in terror as the 33 year-old struck at the house in Bathgate, West Lothian last July 5.
Martin blamed Keith for his mother's death despite there being no evidence that was true.
The killer returned to the High Court in Glasgow on Thursday having admitted to a murder charge in April.
Jailing him for life, Lord Matthews cut the minimum sentence from 20 years due to the guilty plea.
Sentencing, the judge also paid tribute to the two children scarred by what happened.
Lord Matthews told Martin: "They were in the house at the time of this merciless attack.
"I have read victim impact statements and they are heart-rending.
"The 13 year-old boy heard what was happening and felt guilty that he did not stop the attack.
"in truth, the only person guilty was you and, hopefully in time, the boy will be able to come to terms with that.
"As a matter of fact, he bravely did his best to make sure the little girl could not see or hear what was going on.
"He also had the presence of mind to call for help."
Keith had been married to Martin's mum Christina Allan for 16 years.
But, she tragically took her own life last June 9 - just weeks before the killing.
Prosecutor Mark Mohammed said Martin "formed the belief" that Keith was responsible for what happened.
Despite that, on July 1, Martin moved in with Keith having split from his partner.
But, the hearing was told they went on to "argue frequently".
On the afternoon of the murder, Keith told a woman he was "struggling" with Martin living at the house.
However, he decided to give his step-son "one more night".
Just hours later, Martin went on to kill Keith striking him at least 15 times with a hammer.
Two children upstairs had initially been alerted to Keith shouting: "What are you doing to me?"
Martin screamed back: "You should not have done that to my mum."
One of the children was described as "hyperventilating" as he phoned for help.
Keith managed to crawl to the front door despite being under attack.
One neighbour then tried to step in.
But, Mr Mohammed told the hearing: "Keith Allan repeatedly shouted 'help me'.
"Martin shouted to the man: 'It is ok. It has got nothing to do with you'."
A retired police officer also tried to intervene. He spotted Keith lying "half in and half out" the front door covered in blood.
A mobile phone clip of the brutal attack was played at the hearing in April.
Martin at that time refused to look at the screen and sat with his head in his hands in the dock.
The court heard then how Martin called his ex-partner after the killing stating: "I've just done him. I'm really sorry.
"My mum told me to do it. He killed my mother."
Keith did not survive the attack having suffered "extensive head injuries".
A claw hammer was found by police hanging from a fence at the front door.
Jim Keegan QC, defending, today/yesterday said: "His belief was Keith Allan killed his mother.
"That is not supported by any evidence whatsoever. The video played showed a vicious attack in front of an assembly of people.
"He will not accept that his mother committed suicide and he maintains that belief."
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