The Commander of the "Cleaners" designed to remove incriminating evidence of Umbrella's wrong-doings. The leader was in fact Human, and thus one of the select few the Cleaners were programmed not to kill on the battlefield.
As the island was destroyed by the Self-Destruct system, it is unknown if the Leader managed to escape the island before it exploded.
He only appears in one of the game's three possible scenario's. In it, he is killed by the newly awoken Hypnos T-Type.