Cramp found the man, but also encountered Mr Hargreaves, and Cramp reportedly raved that Mr Hargreaves "owes me big time".
Cramp then left, but returned a short time later and demanded that Mr Hargreaves call another worker for him. But, when Mr Hargreaves refused, Cramp stalked him through the plant, climbing on to a truck and cutting the wires to four CCTV cameras so there was no evidence of what was about to happen.
Cramp then pulled a knife from his shoulder bag, slicing Mr Hargreaves across the neck, leaving a 12cm deep wound that severed his spinal cord. The attack was so brutal that a co-worker in the plant at the time hid in a stack of wood pallets and only came out when help arrived some time later. Mr Hargreaves was found with his hand in his pocket, proving it was an unprovoked attack, the court heard.
Sentencing judge Justice Michael Adams said Cramp was a "dangerous individual" who had a history of violent offending, including stabbing a man through a lung, which made rehabilitation unlikely.
Justice Adams dismissed Cramp's claim the ice had left him "not thinking clearly" and sentenced him to 40 years' jail from his arrest date of March 2, 2013. With a non-parole period of 30 years, Cramp will be eligible for parole on March 1, 2043.
Cramp went on the run after the killing, prompting a call from his mother on national TV in Australia for him to give himself up.