A fast-moving apartment fire displaced four adults and four children on Sunday, and reduced at least one apartment in a southwest Colorado Springs complex to a smoldering, charcoal-filled hole.

Firefighters rushed to the Bonterra Lakeside Apartments, 850 Bayfield Way near Quail Lake, around 1 p.m. on Sunday, when residents in a third floor apartment building reported smelling smoke while they were decorating their Christmas tree. The smoke was coming from a second floor apartment directly below, but it quickly erupted into flame, said Josh Poulopoulos, a resident of the complex who was watching the fire from outside.

“You couldn’t even breathe just standing on the stairs,” said Poulopoulos, referring to outside staircase in the same building as the two apartments.

The flames quickly shot out of the window and curled around the building and burned patios on the southwest-facing side, Poulopoulos said.

Nearly two hours later, firefighters were still inspecting the smoking remains of the two apartments; a cause of the fire had not been determined. While the fire started in the second floor apartment, it heavily damaged a third floor apartment and water used to fight the flames damaged a first floor apartment. The occupants of the second floor apartment had been out walking their dog when the fire started. There were no injuries, and only one person was treated for smoke inhalation.

The American Red Cross Pikes Peak Chapter was on hand to assist the displaced residents, one of whom stood on a street corner a couple of hours later crying in dismay and surrounded by people.

Poulopoulos said he had seen the second floor apartment and that it was totally damaged.

“You can see inside the home on the second floor from the ground,” he said.