Deputies say the white Jeep drove through the house, located in the 3400 block of East Lake Sammamish Shore Lane SE, just before 8 p.m. The car ended up partially submerged in the lake.
The 68-year-old woman who was behind the wheel wasn't seriously injured in the crash. Her 3-year-old grandson, who was with her in the Jeep, also escaped injury, according to B.J. Myers with the King County Sheriff's Office.
Myers said three people were inside the house when the Jeep came barreling through. A 70-year-old man, who was the driver's husband, was killed. The driver's 34-year-old daughter and 40-year-old son-in law were both seriously injured in the crash. Both were taken to Harborview Medical Center.
Neighbor Kevin Connelly was inside when he heard the crash.
"The first thing I saw were the two of them on the stretchers in the driveway," he said.
Investigators don't yet know what led up to the wreck, but Myers said it appears the woman was either just leaving or was attempting to park when she drove into the house.
Drug recognition experts are speaking with the driver to determine if drugs or alcohol played a role in the crash.
Detectives from the KCSO major crime and major accident units are handling the investigation and officials from the Department of Ecology are on scene to deal with any fuel in the lake.