Father-of-two Rodney Mitchell tried to stop Dobbie in the third attack.
When Dobbie stuck the gun through a car window, Mr Mitchell got out naked and lunged for the weapon.
He was shot and killed.
«Tragically [he] paid the ultimate price for his bravery in confronting you,» Justice Champion said.
Dobbie then drove off with a woman in Mr Mitchell’s car but she threw herself from the moving vehicle and escaped.
Justice Champion said the victims had suffered «tremendous pain, suffering and trauma, the effects of which have been felt for almost 40 years and will likely continue for many more».
Dobbie fled to Cape Tribulation in far North Queensland after the shooting, remaining there until an anonymous tip to Crime Stoppers in 2018 identified him as a suspect.
Justice Champion said without Dobbie’s confessions in a police interview, the prosecution could not have gone ahead.
He accepted Dobbie was remorseful but noted it took decades to reach the level that prompted confession.
Had Dobbie been sentenced before 1986, the law would have required a mandatory life sentence for murder.