Kirk Persinger was the boyfriend of Angela Montenegro. Every year, Angela took off 3 weeks off from work and went to New Mexico to visit him. Angela mentions spending about 15 weeks with him in total, and that it was her choice not to spend more time with him. He wanted to marry her.
Kirk took peyote for spiritual purposes. In the episode The Skull in the Desert, he was murdered while taking photographs in the desert and his skull was sent to the local police station, prompting an investigation.