Another was a woman born in 1980, who had a toddler and an infant in her vehicle.
The third was a woman of unknown age who was by herself in her vehicle, police said.
The collision happened about 11:20 a.m. at South 320th Street and Interstate 5.
Police said the driver was speeding when the sports car struck two cars making left turns and then hit another two vehicles waiting at the intersection.
Two people were taken to Harborview Medical Center in Seattle. The driver of the sports car suffered minor injuries and was taken to a local hospital.
South 320th Street was closed for several hours while officers investigated the crash.
Anyone who saw the accident or the black sports car before the accident was asked to call police at 253-835-2121.