(Covers information from the S.D. Perry novels)
Dr. Richard Aquino was an Umbrella employee assigned to Raccoon City's largest hospital as a virologist. He was also a member of Operation Watchdog, Umbrella's secret police.
Some time before the t-Virus outbreak in Raccoon City, Aquino began working on a vaccine, something Umbrella opposed. With the help of his assistant, Douglas they succeeded in its development. Umbrella - opposed to the vaccine development project, and taking his lack of reports as proof of betrayal - marked him for assassination by his other Watchdog comrades.
In the latter half of the outbreak, Aquino, the now sole-surviving member of the research team, prepared a meeting for Ken Franklin to pick up the sample. Another Watchdog, Sergeant Nicholai Ginovaef beat Ken to him, however, and impersonated the man to uncover information on the vaccine research. Aquino was not fooled by this and assumed naivety to slip behind Nicholai, hoping to attack him with a syringe. Nicholai quickly deduced that this was an act and turned around to stab him in the throat.