Garry Taylor Handlen has been charged by RCMP in B.C. with two counts of first-degree murder in a pair of cases going back nearly 40 years.

The victims were Kathryn-Mary Herbert, 11, and Monica Jack, 12.

A present day image shows Garry Taylor Handlen, who has been charged with first-degree murder in the deaths of Monica Jack in 1978 and Kathryn-Mary Herbert in 1975. (David Ridgen) ​Handlen remains in custody, RCMP announced Monday at a news conference with the girls' families present.

Herbert disappeared in September 1975 close to her home in Abbotsford, B.C., while returning from a friend's house. Two months later, her body was found hidden under a rotting outhouse on the nearby Matsqui First Nation.

Jack disappeared three years later in 1978 while riding her bike. Her body was not found until the mid-1990s north of Merritt.

Police want to speak with anyone who remembers seeing Garry Taylor Handlen around the time of the killings. This image of Handlen is from the 1970s. (RCMP) RCMP today said Handlen was suspected in the killings shortly after they happened, but police didn't have enough evidence to charge him until now.

Investigators wouldn't specify what the new evidence is, but did say advances in forensic science are a factor.

Police also released a photograph of the suspect, taken around the time of the killings. They're asking anyone who recognizes Handlen to call if they have any memories of him from that time.

Speaking at the news conference, Madeline Lanaro, Monica Jack's mother, said she prayed for decades for her daughter's killer to be found.

"Over the years, thinking about this on a daily basis … even today it's not easy because, no matter what happens and no matter what you do in your life, that hurt never goes away."

Monica Jack was out for a bike ride when the 12-year-old was abducted and killed. She remembers her daughter as a beautiful girl with a distinctive laugh, who was loved by relatives, friends and teachers.

A feature documentary, made for the CBC by filmmaker David Ridgen on Herbert's case, aired on The National in 2009.

It examined flaws in the investigation, including missing files, overlooked evidence and other problems, and highlighted several suspects, focusing mainly on Garry Taylor Handlen, whose identity Ridgen said he knew, but could not mention at the time.

At that time, Herbert's mother, Shari Greer, talked about her frustration with the investigation and her determination to keep police working on her daughter's case.

Today, Greer thanked Ridgen for his documentary and the cold case investigators who took a fresh look at the case and gathered the evidence that led to charges.

"There is no such thing as a cold case to the families, nor is there ever closure, only resolution surrounding the events."

Kathryn-Mary Herbert disappeared 39 years ago in Abbotsford, B.C., after going to dinner at a friend's house. (Family photo)

Watch the CBC documentary by filmmaker David Ridgen from 2009