In a victim impact statement read by the Crown in court on Friday, David Ntahobali described his mother as "the scaffolding" that held their family together over the years.
"Nothing will ever be the same again," Ntahobali said. "We will never be the family we once were."
Ntahobali's statement was read during a sentencing hearing for Adonay Zekarias. He was found guilty earlier this week of first-degree murder in the stabbing death of Ntahobali's mother, Nighisti Semret.
The conviction comes with an automatic life sentence of 25 years, with no eligibility for parole.
Semret, 55, was stabbed to death in the early morning hours of Oct. 23, 2012 as she walked down a Cabbagetown laneway on her way home from a night shift at a downtown hotel.
Semret and Zekarias were both refugees from Eritrea, and Semret had been helping Zekarias with his English.
In court on Friday, Zekarias, 43, made a statement of his own through an interpreter.
"Since there is nothing that I have done, there is nothing that I feel," he said. "Nighisti was nothing but a friend to me."
Zekarias also said he will appeal.
Before handing down the sentence, Justice Ian Nordheimer acknowledged that the reason for the killing remains a mystery.
"Nighisti Semret came to this country from a troubled part of the world. By all accounts she became a hard-working member of society," Nordheimer said.
"We still have a desire to know why this happened. We still don't know, and we may never know."
Zekarias also faces a murder charge in connection with the death of 28-year-old Rigat Ghirmay. Ghirmay's remains were found in a duffel bag in Toronto's west end about six months after Semret's death. Some remains are still missing.