Mr Camilleri, 43, had a heart attack and died after he injected the painkiller fentanyl in his Wodonga unit on December 3.

His father John Camilleri, who lives in Lake Cathie in NSW, had spoken to his son only three days earlier when he thought his son was calling to speak with him again.

“This chap rang me on Mark’s phone and I thought it was him,” he said.

“The minute I didn’t hear Mark’s voice, I knew then, I knew straight away that something had happened to him.

“For all his faults, he was a good kid, he had a big heart and he was kind to everyone.

“He could have been anything, but he wasn’t smart enough to stop hurting himself.”

Mark grew up near Parramatta with his father, mother and two sisters.

“He was a very intelligent kid. Where exactly he went wrong, where he sort of turned, I can’t pin it down for the life of me,” John said.

His parents separated and his mother relocated to Culcairn, but at 17, Mark moved back to Sydney and John said that’s where his drug addiction accelerated.

“That’s the problem, as some kids have today, they get addicted and it’s a downward spiral. Some can sort of experiment with drugs and others get in its clutches and it doesn’t let go,” John said.

Mark was injured in a car crash and he had been on the pension since, moving back to Wodonga 15 years ago.

Despite the ongoing struggle, John said he regularly spoke to his first-born son and their last conversation was typical of their relationship.

“He said ‘Dad, I’m staying out of trouble, everything’s good’. We just talked about the weather generally. I got to the stage at times that I didn’t want to know everything because he’d tell me everything. I got to the stage where I couldn’t help,” John said.

John said Mark, who did not have children, never lost his kind heart and he’d “sooner go hungry” than see his beloved cats go without food.

John called for action to be taken to stop fentanyl from being so easily accessible from doctors for those who want to abuse it.