OLYMPIA, Wash. -

A Washington state prison inmate accused of repeatedly stabbing a corrections officer with a 4-inch homemade knife has pleaded not guilty to a first-degree assault charge.

The state attorney general's office charged Carlos Avalos last month, alleging he approached the guard from behind while the officer was working on a computer in a "staff only" section at the Clallam Bay Corrections Center, then stabbed him repeatedly in the neck.

The state says the attack continued until another officer sprayed Avalos with pepper spray, then managed to handcuff him. The injured corrections officer was taken to a Port Angeles hospital by ambulance.

Avalos is currently serving a 10-year exceptional sentence imposed in 2012 for attacking a counselor at a juvenile correctional facility. His trial is scheduled Aug. 11. The attorney general's office is prosecuting the case at the request of the Clallam County prosecutor.