Sounds like the plane was a regional package freighter aircraft. The Seattle PI
named it Air Pack...but it should have been Airpac. Airpac has several bases along the west coast...just to clarify. They are not just based in the Puget Sound area. They have several planes ranging from Piper Chieftains to Beech 1900C's based out of Boeing Field. They contract with UPS and DHL out of Boeing Field. It sounds like he was making is package hops throughout the Northwest.
My prayers go to the pilot and his family.