The mother of an 18-year-old man killed in two-alarm fire at a Toronto Community Housing complex Monday night has died, her brother has told CBC Toronto.

Abdul Wahid Whahedi says his sister, Fakhria Whahedi, 47, and her 18-year-old child who had lived with autism had been trying to wake up the younger son when flames broke out around 9:30 p.m. in the building near Flemington Road near Allen Road and Lawrence Avenue West.

The 18-year-old died in hospital Tuesday, while his mother and brother remained in critical condition.

The 16-year-old, who has Down Syndrome, was sleeping at the time, Whahedi says on a GoFundMe page set up for the family.

"As a mother, the only important thing to her in that moment of life or death was to save her child," he wrote on the page, adding that the 47-year-old struggled to pull her son from the apartment.

Emergency crews would find all three family members without vital signs.

"The doctors caring for the victims expressed that they believe Fakhria was a hero," the page goes on to say.

Whahedi says that the 16-year-old remains in critical condition on life support, with extensive damage to his lungs and internal organs.

Meanwhile, the boy's father, who had immigrated to Canada from Afghanistan, and the rest of the family are "heartbroken, devastated, and in a state which words cannot describe," the page says.

TCH has said the fire was contained to an apartment on the first floor. Earlier, Toronto Fire Services Capt. David Eckerman stated it started in the basement. Chief Matthew Pegg had noted it was on the third floor.

"Our thoughts are with the family and loved ones of the person who perished in this tragic fire," a TCH spokesperson wrote in a statement to CBC Toronto Tuesday. It added its team members were on the site in the Lawrence Heights area to assist tenants.

For now, the fire remains under investigation. There's no word yet on the cause, but police have said it is not believed to be suspicious.