When Voyager answered his distress call, Donik warned them to stay away. He fired his weapon at them, before Tuvok sneaked up behind Donik and rendered him unconscious with a nerve pinch. Donik had lost a lot of blood, so he was beamed to sickbay. He was the only survivor of the hologram attack.
After being beamed to sickbay, Donik informed Captain Kathryn Janeway that he was on a training exercise when the holograms malfunctioned and took over the exercise, removed the safety protocols and attacked the hunters. At first he was afraid that the crew of Voyager were holograms. Donik told Janeway that he modified the holograms under his Alpha's orders to make them formidable prey and to make them self-aware.
After other Hirogen ships arrived, he was a go-between for the Hirogen and Voyager in an attempt to stop the holograms. He was more comfortable with the crew of Voyager than his own race. He asked to stay aboard Voyager rather than go back with the other Hirogen. He stayed on Voyager during the pursuit of the holograms, and was able to modify the ship's sensors to detect them.
Iden, the leader of the rebellion, was killed and the rebellion was stopped. Donik remained with Kejal, another hologram, on the hologram ship and reprogrammed the holograms to undo some of the damage he had caused as a holoprogram engineer. (VOY: "Flesh and Blood")