Intended as the next step in Hunter development, the "R" replaced the "α" as the development model. The reason for this was to increase "usability", as the practical applications for the "α" was considered to be somewhat limited. This particular variant was being developed in the Raccoon City Underground Laboratory under William Birkin and another Umbrella facility located above-ground. The Hunters in the above-ground facility had been delivered there as part of an experiment with the Tyrant R, testing its strength against several of the beasts.
After Dr. Birkin became infected with the G-virus and went on a wild rampage, numerous "R"s were released, killing a number of Umbrella researchers before the temperature controls were lowered. The Hunters, unable to continue killing in freezing temperatures, froze in their tracks.
However, a group of refugees trying to escape Raccoon City were forced to bring the facility's indoor temperature back up to allow a large elevator to function. The Hunters were then exterminated by the survivors.
Several of these Hunters were found dead in the machine storage room on the third floor of Raccoon University. Two hung from hooks on the ceiling while another was laid out on a table.
They were also a sizeable threat to the refugees hiding in the above-ground facility until Carter, an Umbrella researcher, released the Tyrant R to finally rid the facility of the creatures.