What a threat is, and how it is defined is a matter of law. Some threats when conveyed via the internet may not be a crime, though the same threat conveyed in person and coupled with the apparent ability and willingness to carry it out may be. Without knowing the exact "threat," the means conveyed, and how serious the intended victim might have considered it, it is impossible to say.

You can Google the terms for Washington state and find out what it has to say about threatening communications and the like.