Sheriff's Office spokeswoman Cindi West says a "preponderance of evidence" gathered at the scene shows that is what triggered the crash at SW 136th Street and Ambaum Boulevard SW, at about 8:15 p.m. Sunday.
The driver of the SUV was booked into jail for investigation of vehicular assault. Detectives also took a blood sample from the SUV driver, who is suspected of driving while under the influence of alcohol, West said.
The Snoqualmie Casino Express bus crashed through the wall of a vacant building after it was hit by the SUV. The bus driver sustained severe head injuries. She was taken to Harborview Medical Center, where she is still listed in critical condition.
The driver of the SUV was not injured. A passenger in the SUV sustained minor injuries.
Sgt. John Hall says witnesses also reported seeing a woman and boy running from the SUV.