Teen smirks as he explains how he killed his own mother

The story of Zachary Davis, who murdered his own mother when he was just 15-years-old, is well and truly a chilling one.

After spending an evening at the cinema with his mother and older brother in 2012, Zachary waited until she had fallen asleep and swung at her head with a huge sledgehammer, hitting her over and over until he was sure she was dead.

What makes the horrific murder story even more unsettling is that Zachary has never appeared to show any remorse for the brutal act - in fact, when he thinks back on it, he smiles.

Zachary's mother Melanie Davis, who had been raising her two sons on her own since the death of her husband six years prior, woke after the first blow to the head.

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As she gasped for air and began experiencing seizures, her son continued to strike her head with the sledgehammer.

After he was sure he had killed his mother, Zach next attempted to set his home on fire.

Using a mixture of whiskey and petrol to get the fire going, Zach has claimed his hope was that his brother Josh would burn alive inside the house, alongside his mom's corpse. But Josh smelled smoke and fled the house before it was too late.

In police interrogations that were detailed during his court case, Zachary said that his one regret from that night was that he didn't 'kill josh with a sledgehammer too.'

Zach was eventually convicted of first-degree murder after a four-day trial.

Just two months before his trial took place, Zachary sat down with TV personality Dr Phil to discuss the murder.

Dr Phil

The interview made for a deeply disturbing watch that Dr Phil had to warn viewers about before they dared to tune in.

During the interview, Zachary calmly told Dr Phil precisely how he went about murdering his mother, speaking in an emotionless, monotone voice.

Asked why he decided to kill his mother, Zachary tells Dr Phil: "She wasn't taking care of my family."

He then describes, in detail, what the murder scene was like.

While speaking about what it sounded like when he hit his mother repeatedly with a sledgehammer, he smirked.

"I could just hear the hammer hitting her head. It was this wet thumping sound," he explained, letting out a laugh.

Dr Phil, obviously a bit put off by the inappropriate laugh, asked Zachary: "Did you laugh when you were hitting her?", to which he replies that he did.

Asked why he laughed, Zachary simply replied: "I just thought she deserved it."

Zachary was handed a life sentence for the murder of his mother, plus an additional 20 years for attempted first degree murder and aggravated arson.