SHELTON, Wash. (AP) — Authorities say an inmate in isolation assaulted a corrections deputy at Mason County Jail in Shelton.

The Mason County Sheriff's Office says the deputy was serving lunch to the person in isolation Wednesday when the inmate punched the deputy in the face, knocking him down.

The sheriff's office described the assault on Twitter Thursday as violent, sudden and forceful.

The sheriff's office says the deputy went to a hospital for treatment of minor injuries.

The incident is under investigation.