Victoria Police are set to increase the reward offered to solve the 25 year mystery of the death of Karmein Chan. Courtesy Seven News

THE child abducting murderer known as Mr Cruel stalked Melbourne in the 1980s and has never been caught — but Victoria Police are hoping that’s about to change.

Police are expected to announce on Thursday a massive increase in the reward money that would led to the conviction of Mr Cruel, from $300,000 to a $1 million.

This month marks the 25th anniversary of the abduction and murder of his last known victim, 13-year-old Karmein Chan, in Templestone, Victoria.

“Mr Cruel” is the man behind a number of unsolved crimes against children, including the 1988 and 1990 kidnappings of Sharon Wills, 10, and Nicola Lynas, 13. But it’s believed he is responsible far more attacks, possibly up to a dozen including rape, in a crime-spree that lasted a decade.

Karmein Chan was the only one who was killed. Detectives at the time had a theory she was killed because she was able to see Mr Cruel’s face. All the other victims weren’t able to identify him.

Her body was found a year after she was taken. She was found by a man walking his dog, and had been shot at least three times in the back of the head.

At the time of the abduction Mr Cruel told Karmein’s sisters, who were at home with her when the abduction occurred, that he only wanted their money. He dragged Karmein away by the hair, and she was never seen alive again.

The Herald Sun reported it was possible the rewards in relation to Sharon Wills and Nicola Lynas would also increase, making the total reward a possible $3 million.

If so the case would be the largest reward ever offered in Australia.

Earlier this year former Detective Senior Sergeant Chris O’Connor, who at one time led the manhunt for Mr Cruel, told news.com.au the fact no one was charged still troubled him.

“No one was ever charged. That’s the main concern. With a significant investigation like we had to get to the end of it, 25 years later and we have no resolution for the families,” he said.

The problem for investigators was there was a lack of evidence.

“There were too many gaps in the information ... Clearly, and you don’t have to be a psychologist to know this, but that sort of behaviour is reprehensible ... Clearly the person had severe problems.”

Without anything concrete to go on police struggled to make much progress, despite interviewing thousands of people.

“You can be the best investigator in the world and it may be the best run investigation, but at the end of the day if you do not have avenues of inquiry that are solid, it’s a very difficult that you’re going to identify the person,” Mr O’Connor told news.com.au.

andrew.koubaridis@news.com.au