RICHLAND, WA – The Richland Police Department has confirmed that the driver involved in a fatal collision on State Route 240 near Horn Rapids on March 1 was an off-duty Washington State Patrol (WSP) trooper. The trooper, identified as Sarah Clasen, has been arrested for DUI Vehicular Homicide and booked into the Benton County Jail.

Richland police officers were initially dispatched to assist WSP at the scene, as they frequently do with other collisions near their jurisdiction. However, once it was determined that an off-duty WSP trooper was involved, WSP requested Richland police take over the investigation to ensure independence.

Clasen, a 14-year veteran of the agency assigned to the Yakima field office, was placed on a 72-hour hold for Vehicular Homicide. The Benton County Prosecutor’s Office will review the case once the investigation is complete.

WSP previously addressed inaccurate reporting from a local media outlet, which had incorrectly identified a different trooper, Matthew D. Mason of Benton City, as the driver involved. The agency clarified that no such trooper exists and that Matthew A. Mason, a WSP trooper from Bellevue, had no connection to the incident.

The investigation remains ongoing. Richland Police Commander Chris Mason is handling inquiries and can be reached at 509-942-7360.