The grieving mother of a boy who died in a fire while sleeping over at a friend's house in Brampton, Ont. is confronting a parent’s worst nightmare.

"I can't understand how someone can grab their own child out of the same bed my son was in and leave my son there," Kelly Gabriel told CP24 on Sunday.

Police said a fire broke out while a man was cooking, at 3:15 a.m., in the townhouse where Gabriel’s 10-year-old son Nicolas was having a sleepover.

The man's son was saved, firefighters told CTV Toronto, but Nicolas Gabriel was not.

Dylon Kyest lived in the unit across from where the fire started. Kyest told CTV Toronto on Monday that he kicked in the unit's door, and found a man asleep on the couch. Kyest was able to rescue the man and his son, but did not know another boy, Nicolas, was asleep upstairs.

"I might've been able to get him out," Kyest said.

Kelly Gabriel said she was awoken by a friend banging on her door, who told her that there was a fire in the unit where her son was staying. She ran outside and watched the fire destroy the townhouse complex.

"I was out there watching the whole thing go up in flames, not knowing where my son was," Gabriel told CP24 on Sunday.

At approximately 8:30 a.m., she received word that a child's body had been found in the home.

"He was my baby," she said.

Gabriel has two other children, and said her family is struggling to come to terms with the loss. She said her 6-year-old has been asking for Nicolas, and her 14-year-old daughter is blaming herself because she and Nicolas had fought before the fire.

"I can't ask for my son back. All I can ask for is for everyone to think and pray for us."

Nicolas’ father Shane Gabriel posted a Facebook tribute to his son on Sunday night.

"Why did you leave us? I miss you so much," he wrote, adding that he already misses his son's questions: "Are you happy with me? Are you proud of me?"

"Nicky- I was ALWAYS happy and proud of you; no matter what," he wrote.

The heartfelt message has since been deleted, and replaced with a message saying, "In case you all haven't heard.... We lost Nicolas today. We love you Nicky!"

On Monday, Tanya Garvey, the mother of another little boy who died in the same area, came to pay her respects. Nine-year-old Keesean Williams was shot in the same townhouse complex in January 2013.

"I know what it feels like, and it's awful," Garvey told CTV Toronto.

Police said an estimated 18 housing units were badly damaged or destroyed in the fire, leaving 80 to 100 people without homes.

It is believed that the fire began in in the kitchen of the townhouse where Nicolas Gabriel was staying, and transferred through a shared roof to the neighbouring units.

Witnesses said the fire spread quickly along the roof. "Within seconds it was engulfed," Brian Mitchell, a local resident, said.                        

"The townhomes today under building code are required to have fire separations every so many units to stop this thing from happening," Brampton Fire assistant division chief Gary Jarrett told CTV Toronto on Monday. He added that as the units were older ones, it was uncertain if the building adhered to those codes or not.

Two trust funds have been set up to support the residents affected by the fire. Donations can be made to Giving to Ardglen or Nicolas Gabriel/Ardglen Trust Fund.

Another trust fund has been set up by coworkers of Kelly Gabriel to fund the boy's funeral. Donations can be made here.

With files from CTV Toronto's Austin Delaney.