The Supreme Court heard Burton had threatened Auckram and his wife and Auckram thought his stepson may have had a weapon at the time of the shooting.
Justice Ralph Simmonds sentenced Auckram to four years and 11 months jail but suspended it for 18 months. He took into account the 13 months Auckram had already served in custody and that he had throat cancer that required radical surgery.
Police prosecutors have appealed the sentence and a hearing is scheduled for September 13.
Since his son's death, Jeff has had trouble sleeping and is haunted by how his son died.
"I don't understand how Bradley could do that. How can you shoot someone like that, in the arm, twice in the back and then in the head and not be in prison?" Burton said.
"It wasn't necessary. Jason was not armed. He was holding a cup of coffee."
Jeff described his son as a lost soul, who went from being a soldier in the army to joining a monastery. Jason, his brother and sister, were raised in Papakura until their mother Jacqueline met Auckram through work and left her husband.
Jeff said Jason was only 8 at the time of the split and struggled to accept then 18-year-old Auckram as his father.
Auckram told the court he felt threatened by his stepson, who had threatened to "slaughter" him on the day of the killing.
Jacqueline, Burton's mother, supported her husband throughout the trial and said she, too, had been scared of her son.
Jeff said he had struggled with Auckram's comments that he had killed Jason because he was "protecting his family".
"He had Jason, my son, since he was 8 - wasn't Jason part of his family?"
Jeff flew to Perth for his son's funeral and said he was distraught he couldn't see Jason to say goodbye.
"It was a closed casket because he was so badly damaged. He had been shot in the head so there was not much they could do."
The funeral service was attended by 10 people and there was no funeral notice. "It was like they just wanted to forget all about it."
Jeff said he would not rest until justice had been done for his son.
"I want Bradley to go to prison for what he has done. That is the fair thing."