The Washington State Patrol tells KOMO News' sister station KEPR the couple was having an intense argument while driving on the freeway eastbound.
The husband told troopers his wife told him it wasn't safe to be driving while they were having such an escalated fight. The husband told WSP he didn't want to pull over but then lost concentration on the road and drove off the interstate near Road 100.
His wife, Cynthia Bynum, was thrown through the windshield and killed.
It's believed the 43-year-old woman was from Richland.
Hours later, WSP troopers still had a lane blocked off to investigate the accident. Officers cannot say just yet if drugs or alcohol were involved.