The Underland - S1E5 - Matthew Charles Johnson

Carl Williams was serving a life sentence, with a minimum of 35 years before he would even be considered for release. From his cell in Barwon Prison, he became an unlikely informant. Williams had begun assisting police, feeding them information that threatened to unravel long-buried crimes and expose those who thought themselves safe.
But in the underworld, cooperation with authorities carries a price. On 19 April 2010, that price was paid in blood. Williams was beaten to death inside Barwon’s high-security Acacia unit, struck with the metal stem of an exercise bike. His killer was another inmate—a man already notorious, with his own violent history etched deep into Melbourne’s crime story.
That man was Matthew Charles Johnson.