Crews responded to the scene, in the 3600 block of 34th Avenue South, at about 12:15 a.m. Sunday after being alerted by an automatic fire alarm, said Sue Stangl of the Seattle Fire Department.
The flames had been mostly extinguished by the building's sprinkler system when firefighters arrived, but there was extensive water damage and lesser fire damage to one seventh-floor apartment unit from the sprinkler.
Young mother Elisha Estep, who lives in the damaged apartment, said she and her three daughters weren't home when the fire started. She arrived there before firefighters got to the scene. And when she unlocked the front door, she was confronted with a startling surprise.
"I opened the door and my entire house was full of smoke," she said.
Water from the built-in sprinkler system had flooded the unit. Estep, who had been away from the apartment all evening, ran to safety.
Luckily her three young daughters were under her mother's care - far away from the fire.
"I was just panicked ... started freaking out, crying ... everything for my kids is here - the clothes, their toys, their house," she says. "Having three kids, being a single mom, and having to start over is not easy thing."
Fire investigators say the fire started on Estep's bed.
"I have no clue how or who could have done it. It's just a pretty scary thing," she says.
Spangl said fire investigators who arrived on scene determined that the blaze was purposefully set and turned the investigation over to the Seattle Police Department.
Renee Witt of the Seattle police later called the fire "suspicious" and said it was inconclusive whether the fire was intentionally set.
She said the boyfriend, who had been thrown out of the apartment this morning, was contacted by police one block away from the fire. He was questioned and released pending further investigation.
Witt said the fire remains an open and active case. Anyone with information is asked to call 911. Anonymous tips are welcome.