Charged: This picture shows Zachary Davis in 2012 when he was arrested aged 15 for the murder of his mother and attempted murder of his brother . A Tennessee teenager on trial for murder says he killed his mother with a sledgehammer because she knew he had been raped by his older brother and did nothing about it. Zachary Davis was fifteen when he bludgeoned his mother's skull 12 times as she slept and then set his family home ablaze in an effort to also kill his elder sibling Josh. On Tuesday, a court in Hendersonville heard how Davis, now 17, laughed as he killed his mother Melanie Davis in August 2012, leaving her bloodied and unrecognizable before fleeing. Davis is charged with first-degree murder, attempted first-degree murder and aggravated arson and the court was shown gruesome images of the crime scene as his trial began on Monday. According to prosecutors, Davis, his mother and brother went to see the comedy movie, The Campaign on August 10 and then returned home. Melanie Davis went to sleep at 9pm, 'not knowing that her younger son was planning something sinister, something unspeakable.' In testimony given to the court by Major Don Linzy, Chief of Detectives at the Sumner County Sheriff's Office, Davis confessed after he was apprehended at a convenience store eight miles away, having fled the scene. 'Yes, sir, I killed my mom in her sleep with a sledgehammer,' Linzy told the court on Tuesday according to the Tennessean. Linzy said that during his interview Davis was asked why he killed his mother with a sledgehammer and replied, 'I was worried that I'd miss,' and that using that type of weapon gave him the 'highest chance of killing her.' Battered: The teen's single mother Melanie Davis, 46, was killed with a sledgehammer while she was sleeping in her bed . Shockingly, Davis told Linzy during his confession that he he laughed out loud for no reason he could remember during his frenzied attack. He also said he only had one regret from that night, 'I would probably kill Josh with a sledgehammer too.' However, during his interrogation, Davis did tell police why he brutally killed his mother and tried to kill his brother by burning down the house. Linzy told the court on Tuesday that Davis alleged his brother, Josh raped him and that he told his mom, 'who didn't do anything about it.' Josh Davis vehemently denies ever sexually abusing his family and Linzy told the court law enforcement came to the same conclusion. 'We started a child protective team to see if it happened,' he said according to the Tennessean. 'We did not have anything to corroborate Zach's statement.' Mental illness: Zachary Davis legal team admit that their client burned his own house down and killed his mother but was suffering delusions at the time . Indeed, Josh Davis, 19, spoke in court on Tuesday and saw his brother for the first time in two years. He told the prosecution that he and Zach were close and said that until the shocking murder his entire family were all close. He said that he, Zach and his mother had bonded after the death from their father from ALS in 2007 and the first he knew of his brother's murderous intentions was on the evening of August 10. He told the court he awoke to the sound of the smoke alarm and ran to his mother's room but found it was locked. He said he broke the door down to find her dead and ran to his neighbors' home for safety. Sumner County District Attorney Ray Whitley said that on the night of August 10, Davis packed a backpack with notebooks, a toothbrush, gloves, a ski mask and a clawhammer and readied himself. Horrific: On the night of August 10 Davis allegedly attacked his mother before moving upstairs into their home's game room, pictured, where he lit a fire, hoping to kill his sleeping brother as well . Far beyond: Davis is seen here in 2012: It was determined that his charges were so severe that he would not be charged in juvenile court . 'Zach Davis had planned and intended to kill his mother and brother, and tonight was the night,' said Whitley according to the Tennessean. After killing his mother, he set fire to an upstairs room using gasoline and whiskey but closed the door and the fire did not catch as he intended. Defense attorney Randy Lucas has asked jurors to listen to all the evidence before they reached their verdict, despite admiting that his client did kill his mother. Lucas will argue that his client was suffering from mental illness. 'The voice of his father told him to kill his mother,' said Lucas to the court. A volunteer firefighter, Winton Batson, told the court how he rushed into the home to try and rescue anyone inside. He said he found his way to Melanie Davis' bedroom and saw her body. 'I saw immediately that there had been significant trauma to her skull,' he said.
Zachary Davis, 17, is on trial for the murder of his mother and attempted murder of his brother .
Brutally bludgeoned Melanie Davis to death in her own bed in August 2012 .
Then set fire to the family home in an attempt to kill his older brother Josh .
The teen confessed to the arson and murder but alleged sexual abuse .
Police have found no evidence of rape and Josh Davis, 19, has denied it .