Lamb, 52, has been charged with second-degree murder in the deaths of Tanya Nepinak, 31, Carolyn Sinclair, 25, and Lorna Blacksmith, 18 — three women who had gone missing within the past year.
But last month, Winnipeg police charged Lamb with sexually assaulting a teenage girl.
Her mother, who CBC News is not naming to protect her daughter's identity, says she has been hit hard by news that the man accused of assaulting her child has also been charged with murder.
"I was in shock," the mother said in an interview, adding that she often thinks of the families of the three dead women.
"The pain that I'm feeling and the shock and these emotions are nothing compared to what they must be going through. And I'm just ... I'm so sorry."
The mother says her daughter is currently in a treatment program, but in October the teen was struggling with drug addiction and was vulnerable.
According to her mother, the teen met Lamb on a street behind a downtown Winnipeg shopping mall, where he allegedly lured the girl back to his Notre Dame Avenue apartment with the promise of drugs.
It was in the apartment that the teen was assaulted, according to her mother.
The girl's mother said her daughter ran away when Lamb briefly left the suite.
Lamb was charged this past spring with sexual assault, sexual interference and obtaining the sexual services of a person under the age of 18, in connection with incidents that date back to October 2011, court records show.
Lamb was arrested in April, but he was released on a promise to appear in court. He was formally charged on May 9, but he was not held in custody.
Instead, the court ordered Lamb not to have any contact with the victim and not to go to any parks, playgrounds, schoolyards and community centres. He was also ordered to stay away from alcohol and drugs.
Feels guilt, anger
Lamb was arrested on June 21 in connection with another sexual assault, this time involving a 36-year-old woman.
That was when Winnipeg police say they learned of his alleged connections to the deaths of Blacksmith, Sinclair and Nepinak.
The teenage victim's mother said she is grateful her daughter escaped from Lamb alive, but her thoughts often turn to the women who did not survive.
"There's also almost like a guilt about it because why couldn't those girls have been able to go home?" she said.
The mother said she is also angry with Winnipeg police for not notifying her or her daughter when Lamb was about to be charged with murder.
"She met with detectives, she identified him, but she didn't even know his name," she said.
"She was told that if he if he ever breached or if he was ever in custody or if anything happened in connection with him, she would know about it ... and they still haven't."
Denied parole repeatedly
Records show that Lamb has 109 criminal convictions dating back to 1979 in Ontario, Alberta, British Columbia and Manitoba.
His convictions have mainly been for offences such as robbery, forgery, fraud, theft, assault, uttering threats and breaching court orders. However, he was sentenced in 1992 to four years behind bars in Alberta for sexual assault.
Lamb has been denied parole at least twice, and on two other occasions his statutory release from prison was cut short by new criminal charges, according to Parole Board of Canada documents obtained by CBC News.
"This is far from your first offence as the board notes an extensive criminal history which spans some 30 years and which shows no significant break," the parole board said in 2006, when it denied Lamb both day and full parole.
It also noted that Lamb has a history of ignoring court orders and release conditions.
"Your severe substance abuse, which is at the root of most of your offending behaviours, remains unaddressed during this period of incarceration, and your motivation is questionable when we look at your behaviour within the institution," the ruling states.