You have it backwards. He himself was using the prescribed grievance process. According to much older stories, it was one or more supervisory personnel in the O-DOT that passed their "fears" to the police.
I don't know any of the key words or titles to look it up, but I read it (posted on FR) as a news story right after it actually happened.
Now it appears "several coworkers" were afraid of him: coworkers had reported frequent outbursts by Pyles. It goes on to say that after learning of Pyles gun purchases, several ODOT employees left their homes and went to motels.
And here is the Medford Mail Tribune's initial story about it: Police act swiftly after gun purchases
There just barely might a thin coating of Teflon on the cops. My personal opinion is that the O-DOT a-holes should be hung out to dry, and the cops need a good knuckle-busting by the courts, as well.