Greenough massacre still haunts WA police DETECTIVES who captured the man responsible for the Greenough family massacre more than 20 years ago are still haunted by the horrific crime, West Australian Police Commissioner Karl O'Callaghan says. William Patrick Mitchell will be up for release from prison later this year, as the state's parole board considers whether he has served enough time for the 1993 murders of 31-year-old Karen MacKenzie and her three children, Daniel, 16, Amara, seven, and Katrina, five. A childhood friend of Amara has begun a petition urging authorities to keep Mitchell in jail, which local MP Ian Blayney has said he will present to parliament. Mr O'Callaghan said he was sure police would have a say on Mitchell's potential freedom. That would include whether they believed he could be adequately managed in the community. "It was a very horrific crime, and the parole board will no doubt be considering this," Mr O'Callaghan told Fairfax Radio. We would make representations and no doubt, if he was given parole, there would be an offender management process to go through after his release. We would have to be certain we could manage that. The four family members were hacked to death with an axe by Mitchell, who was known to Mrs MacKenzie, with the details of the crime so gruesome parts of them were sealed by a judge. Mr O'Callaghan said police were confronted by the scene at Greenough, near Geraldton. "Psychologically it affected many of the investigators who went there, and some of them have not gone back to investigating that type of crime," he said. Mitchell was transferred to medium security at Bunbury Regional Prison in 2009 and will become eligible for parole from October 13.