NSW cop killer 'deeply and terribly' sorry The mother and son who killed decorated cop Bryson Anderson wish they could turn back the clock and stop the tragedy that has led to so many lives unravelling. But the brother of the slain detective inspector says they will never be forgiven. Murderer Mitchell Barbieri, 21, kept his head bowed and wept in the dock as Det Insp Anderson's family and colleagues described to the Supreme Court the trauma of losing a loving, compassionate and hardworking husband, son, brother and friend. The policeman died after he was fatally stabbed by then 19-year-old Mitchell following a protracted siege at his mother Fiona Barbieri's rural Oakville property in Sydney's northwest on December 6, 2012. Mitchell has pleaded guilty to murder while his mother Fiona, 46, has pleaded guilty to manslaughter on the basis of substantial impairment. Det Insp Anderson's colleague James Garey described the ongoing trauma of seeing him take his final breaths. I saw Bryson's face just before he died ... the next 12 months were free-fall. Food lost its taste. I could only taste death and blood," he said. Det Insp Anderson's father Rex said he thought, as a former police officer himself, he was immune to shocking details. But nothing prepared him for the call in which he discovered his son had been murdered. "The events were the most shattering experience in my entire life," he said. Det Insp Anderson's widow Donna spoke of the loss of her best friend while his colleague Adam Fitzgibbon is plagued by guilt. "I ask myself, 'What gives you the right to have good times?'," he said. As Mitchell sat red-faced and his mother tried to console him, Det Insp Anderson's older brother Warwick said to them: "You should save the tears that you shed in the dock. You will not be forgiven. On the day of Det Insp Anderson's death, the court heard Fiona - who suffers from paranoid schizophrenia - had deeply entrenched delusions that she was being prosecuted by a number of bodies, including American Express, police and a number of political figures. These delusions, had to some degree been transferred to her son. In a letter penned to the court, Fiona said: "I would do anything to be able to turn back the clock. My behaviour that day set a poor example for my own son and I have to live with the knowledge that I have ruined his life too. In his letter Mitchell said he thought about it every day and night in prison. Dotted with hand-drawn sad faces, the letter adds: "I could not ever expect that you would be able to forgive me ... but I want you all to know how deeply and terribly sorry I am."