Dr.Logan Carlisle worked as a researcher for Umbrella Pharmaceuticals in one of its secret labs and headed its secret research into biological weapons.
Carlisle successfully finished the development of Hunter Gamma project, a variant of Umbrella's Hunter project, but upon completion, the company rejected it and deemed it a failure.
Some time before the virus completely overtook the city and turned larger population into the undead, Carlisle and other researchers managed to save several Hunter Gammas from being destroyed and smuggled them out of the lab to the Raccoon City sewers. What happened to the researchers is unknown but by the time former S.T.A.R.S. police officer Jill Valentine ventured into the sewers in her attempt to shake off her pursuer, B.O.W. known as Nemesis T-type, a Tyrant enhanced with NE-alpha parasite, she found the sewers empty but populated by several Hunter Gammas. There she also discovered that Carlisle became infatuated with his creations, referred to them as if they were loved ones, noted that they were friendly to the staff but nonetheless acquired military-grade weapon from Kendo Gunshop in event that Hunters will get out of control and attack him and other researchers.