Prin had worked on Bajor during the Cardassian Occupation but was not a member of the Cardassian military, rather a civilian servant. He was horribly disfigured in an attack by the Bajoran Resistance and he believed himself an innocent victim of the attack. He harbored a desire for revenge for a number of years, until in 2373 he began systematically murdering the members of the Shakaar cell responsible for his injury, using hunter probes he directed from his home on a planet near the Demilitarized Zone.
His first victims were Latha Mabrin, whom he killed with a hunter probe hidden inside a candle holder during prayers at the Calash Monastery, and Mobara, whom Prin killed by planting a micro-explosive behind his ear as he slept. Prin then planted a Romulan remat detonator on Trentin Fala, which killed her when she was transported aboard a Starfleet runabout. After each murder he sent a message announcing it to Kira Nerys- using old recordings of her voice after heavily modifying them-, whom he was saving for last because she had been the one to actually plant the bomb that had scarred him.
Another of Prin's hunter probes then traveled to Deep Space 9 by attaching itself to a Talavian freighter. It began scanning the station for Prin's next intended victims, Furel and Lupaza. When it detected them in Kira's quarters, it attached itself to the window and exploded, causing an explosive decompression.
Using a list of suspects gathered by Odo, Kira arrived at Prin's residence but was captured. Prin explained to her his actions, claiming his moral superiority over her by his careful choice of victims versus her "indiscriminate killing". Due to this conviction, he also intended to remove the unborn Kirayoshi O'Brien from Kira's womb before he killed her. Prin agreed to sedate Kira for the procedure, not knowing that she was taking makara herbs for her pregnancy that would neutralize the sedative. Thus, Kira was able to surprise and shoot him after he released her restraints.
See "The Darkness and the Light" under Star Trek: Deep Space Nine - Season 5 Extras for Prin's victims.