The victims were found at a Highland Park house in southwest Seattle. The shooter was described as an Asian woman who was wearing a white shirt and gray sweatpants, The Seattle Times reported quoting police.
The police said one of the victims -- a 42-year-old woman -- suffered three gun shots. At least one person was also injured in the incident.
Someone from the house called 911 and reported his grandmother was mentally ill and had opened fire, they said.
According to a woman at the scene, two families with a total of 11 people were living in the house. Another witness said that a girl came out of the house yelling "she's crazy, she's crazy".