Convicted serial killer Clifford Robert Olson is dying of cancer and has only days to live, according to the families of some of his victims.

Sharon Rosenfeldt says Don Head, the commissioner of Corrections Canada, called her on Tuesday with news of Olson's fading health.

"He has cancer that has metastasized, which means that … he is expected to die within the next few days," she told CBC News on Wednesday morning.

Olson, who is now 71 years old, was transferred from a maximum security prison in Quebec to a hospital in Laval, Rosenfeldt said she was told.

Corrections Canada spokesman Alain Charette said he could not confirm the health or location of any inmate, including Olson, for privacy reasons.

But Ray King, whose son Ray Jr. was murdered by Olson, said he also learned Tuesday that Olson is in the final stages of cancer and could die at any time.

"I was thinking, finally....it's about time...it should have happened 30 years ago...I was thinking maybe at last we'll get a break from him constantly interfering in our lives. It will give us a chance to heal, which we haven't in the past 30 years," said King.

Olson is one of the most notorious serial killers in Canadian history. In 1982 he confessed to 11 killings, male and female victims as young as nine years old around the Vancouver area, including Rosenfeldt's son, 16-year-old Daryn Todd Johnsrude.

Bittersweet news for family

Rosenfeldt, whose son 16-year-old Daryn Todd Johnsrude was killed by Olson, said the news is stirring up conflicting and powerful emotions for her and her family.

"It's pretty bittersweet. I'm still in shock. Will it really be over?" she said.

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"I don't know how to feel, I don't know. It's almost like sacrilegious if I feel pleased that somebody is dying. We've been conditioned not to feel like that, but I don't know. It's really confusing in my mind right now," she said.

"I guess my son summed it up. He said, 'You know Mama,' he said, 'Clifford Olson may be dying and he will be dead. It won't bring Daryn back. We haven't got Daryn.' But...the biggest thing is he won't be able to hurt us again. After 30 years, he won't be able to hurt us.'"

Olson was sentenced to 11 concurrent life sentences, after he was paid $100,000 by the RCMP to lead them to the bodies of his victims. That money was later put in trust for his estranged wife and son.

Olson never expressed remorse for the killings, and was classified as a dangerous offender, meaning he could be held in prison for life.

But under the faint-hope clause he first applied for parole in 1997 after serving 15 years. He was denied parole several times until 2010, when he said he would never apply again.

News that he was entitled to Old Age Security and the Guaranteed Income Supplement of $1,100 while behind bars provoked outrage among the public and politicians in 2010.