The Hirogen programmed the prey to act and fight more realistically, eventually designing a subroutine to simulate the ability to feel pain. Combined with an ability to be regenerated after a simulated death, the holograms began to advance cognitively and became self-aware. The stress of pain created a much greater will to live among the holograms, and they eventually began to question their servitude and victimization.
On stardate 54315, a group of Starfleet holograms managed to win against the Hirogen hunters, killing 43 on the station. A distress call was received by the nearby Voyager, the ship which originated the holo-technology, and a responding away team discovered the various Hirogen corpses, murdered with Starfleet phaser rifles, Romulan disruptors and Klingon bat'leths.
One survivor, Donik, was found.
The holograms, led by Iden, rebelled against the Hirogen and escaped from the confines of the space station on which they resided. Following their successful rebellion, they attempted to create their own colony. Iden's program was eventually destroyed when he became unstable and megalomaniacal, but other holograms assumed leadership of the colony. (VOY: "Flesh and Blood")