Neighbours have identified the victim of a massive fire at a downtown Toronto building as a 22-year-old man.

William Secord Mattson died on Monday when a fire tore through 160 Bathurst Street in the early hours of the morning.

The blaze spread rapidly through the building and was eventually escalated to a five alarm. Firefighters were met with heavy black smoke and flames shooting from the roof when they arrived and endured treacherously cold temperatures throughout their efforts.

Mattson and another person were pulled from the burning building by firefighters. Both were rushed to hospital, but Mattson did not survive.

The second victim remains in hospital in serious condition.

Mattson lived in the basement apartment where he was found, and where investigators believe the fire originated.

He lived in the building with his mother and stepfather.

“I can tell you that we know the family. I saw William around quite frequently. It’s a wonderful family, they’re a hardworking part of our community,” neighbour Christine Whittick told CTV News Toronto.

“His stepdad, Adam, ran the barber shop next door… They were basically just trying to take care of their son, contribute (to the community) and run their business.”

The fire snaked through neighbouring buildings before finally being brought under control by late morning.

A long-time barber shop, considered a neighbourhood staple, is among the buildings impacted. Neighbours say Mattson’s stepfather took over the shop from its original owner and had been renting it and working at it.

Toronto Fire Chief Matthew Pegg described the fire as “difficult” and “intense.”

“It escalated and grew very, very quickly,” he said at the time. “When we’re in the downtown core like this and in an urban environment where the exposures are so tight, it becomes a real challenge for us.”

Tenants of adjoining buildings told CTV News Toronto that they were alerted to the fire by newly-installed smoke detectors. All managed to escape before the fire spread.

The cause of the fire is not yet known. Investigators with both Toronto Fire Services and the Ontario Fire Marshal have been tasked with determining the source.