The Stress Man was a diplomatic attache.
The man traveled to Georgia and Russia and came into possession of a soil sample containing the black oil. He carried it into the US via Honolulu in a discrete diplomatic briefcase without appropriate paperwork, expecting to not be searched. To his surprise, the customs agent directed the man to Border Control, where an officer proceeded to open the briefcase by force. The Stress Man objected frequently, but the officer ignored him, then carelessly handled and dropped the container. The black oil infected the officer. (TXF: "Tunguska")