Tenants spotted the flames shooting from the stairwell of the Brightwater Apartments just after 1 a.m.

"We heard this roaring noise. We opened the door. It was big flames. We panicked and immediately started calling 911," said resident Matthew Martinez.

The flames spread quickly and soon the two-alarm fire blocked any escape.

Neighbors said a woman and her two children were briefly trapped. Thanks to quick action by firefighters they got out safely.

A woman was rushed to Harborview Medical Center in Seattle with second-degree burns on her back and hands.

Friends said she fell in hot debris from the fire.

Investigators don't know the cause of the fire, but tenants said they suspected it started in a baby stroller.

"I called police, and a lady was just standing there and the lady like just walked the other way," said Nikki Ferreira, a resident.

A damage estimate has not been released yet.