A relative of notorious Australian serial killer Ivan Milat, who slaughtered seven backpackers in the 1990s, was Friday jailed for at least 30 years over the brutal \"thrill kill\" axe murder of a boy. Matthew Milat, who pleaded guilty, was sentenced for slaying a friend in the same forest in the southern highlands of New South Wales state in which his great-uncle dumped the bodies of his backpacker victims. The 19-year-old\'s accomplice, Cohen Klein, who also pleaded guilty to murdering David Auchterlonie on his 17th birthday, was jailed for at least 22 years. \"This was a thrill kill on the part of Milat,\" said New South Wales Supreme Court judge Jane Mathews of the murder, which was recorded on a mobile phone. \"He took the life of an innocent young man who was unfortunate enough to be his friend in an unimaginable, cruel, brutal and violent manner solely for his own personal enjoyment.\" The court heard Milat had said he was going to commit a murder, but his friends assumed he was joking. Klein and another teenager who has not been charged drove with Milat and Auchterlonie into the forest in November 2010. Milat at first swung an axe into the victim\'s torso and accused him of telling people about a theft he had committed. Auchterlonie was then told to lie face down on the ground as the killerthreatened him for 10 minutes, saying: \"You move, I chop your head off.\" The phone provided chilling audio of the victim sobbing and begging \"don\'t do this to me\", then records the sound of an axe hitting him. Ivan Milat was sentenced to life in jail in 1996 over the backpacker murders after sensational evidence from Paul Onions, a British hitchhiker who escaped death in 1990 by jumping out of Milat\'s vehicle when he pulled a gun on him. Onions reported the incident to police at the time but years later when he saw news reports of bodies found in Belanglo, contacted the Australian High Commission in London, eventually providing crucial evidence to the trial.