Mr Wilkinson's mother Beverly Lawrie told a media conference today that her son had the option to wear the stab-proof vest when he was trying to place a tracking device on a car outside a suspected P-lab in Mangere on September 11 but chose not to.
Mr Wilkinson, 47, and a colleague ran away when they were disturbed by the occupants but were followed and shot with airgun.
Mr Wilkinson died immediately but his partner, 44, wearing the vest, who was shot several times survived.
He has since been discharged from hospital after undergoing surgery.
A post-mortem examination concluded Mr Wilkinson was shot numerous times and died from a shot to his chest.
"On the morning he was killed he was issued with stab-resistant jacket but by choice he didn't wear it," Ms Lawrie said.
"It may not have saved his life if he had been wearing it."
Ms Lawrie described her son as a very private person who enjoyed his own company and outdoor activity.
She said he was very keen on squash, cycling, sailing and tramping and had been parachuting several times, but would get away from crowded situations, saying "it's too social for me".
"It's always sad when you only have one child, but you're very proud if your only son or your only child lived every moment of his life the way he wanted to do it," Ms Lawrie said.
"He liked to live on the edge. He could because he was not married, but I think the reason he wasn't married is because his job was what it was."
Mr Wilkinson was a radio technician who had worked at New Zealand diplomatic posts abroad and for the United Nations in Bosnia and Somalia.
Ms Lawrie said he had spoken about settling down on his return to New Zealand but soon took on his job with the police, one he told only a very few people about, including his mother.
"If Don was ever asked about his job he said 'oh, a bit of this and that, and a lot of paperwork', or 'I install security systems,' which might be a misnomer in some ways, but I think it's probably right," she said.
"He'd pass it off and go and talk about other things."
Though they did not talk specifically about the dangers of his job, Ms Lawrie was aware it was a dangerous job.
She said she was sure it was her son who died when hearing on radio on Thursday that an officer was slain putting a tracking device on a car.
"I knew it was Don, and I sat down again and waited for the knock at the door. The knock came 10 minutes later.
"Senior Sergeant Kevin Hooper came to the door and I said 'you're early, you don't start work till eight o'clock, Donnie's dead'. And he said 'yes, I'm sorry Bev, Don is dead'."
Ms Lawrie will deliver the eulogy at her son's funeral on Thursday, saying she has to remain strong for all his friends and family.
She said she appreciated the kind words from his colleagues and friends and was moved by tributes written to him in a book at the Manukau Police Station.
She is also looking forward to meeting the officer who was injured when her son was killed.
"He is absolutely upset, as are some of the others, and I'm going to meet them tomorrow privately."
