Gordon Amherst is the individual behind the Green Poison, or Dollar Flu as some NPCs refer to it. His whereabouts were unknown until the end of the game when he is found dead in an empty laboratory. If the player use a scope to look at his face, they'll notice that the scientist was probably killed by his own disease, as there are pimples all over his face.
Jessica Kandel had contempt for him prior to the outbreak, and some of his viewpoints and speeches nearly caused a riot at a campus.
His explanation for creating and spreading the Green Poison was that humanity was too powerful on a global scale, mother nature needed help in "advancing her creations", that humans eventually needed to be put in check, and he was the cure for it. Furthermore, he is also a believer in the concept of natural selection that the strong are the only ones that deserve to live, not the weak, and his creation is the tool to ensure that concept happens since the strong will survive the virus while the weak cannot. With the breakthrough of digitizing DNA, the process of growing a generation of lab-grade pathogens could be done a thousand times faster than conventional methods. Intrigued by this, he obtained smallpox strains from Vitaly Tchernenko and utilized a 3D biological printer to create Green Poison. He ironically died to his own creation, which he infected himself with to live up to his view point of natural selection.