josh mankiewicz (voiceover): finding david strickland was now veuleman's priority according. or, strickland left utah after his arrest and returned to texas. so detective veuleman did the same, hoping this man would turn out to be the investigation's third and final person of interest. craig melvin (voiceover): coming up. a suspect, not acting at all like you might expect. so it's like a game? very much so a game. he was enjoying this interview. craig melvin (voiceover): maybe police have the wrong guy again. she doesn't know who shot her. she has no recollection. she wasn't able to pick our client out of a photo lineup. she wasn't able to point at him in court and say that's the guy that did it. craig melvin (voiceover): when "dateline" continues. welcome back. a mysterious letter had identified christobal melchor as the man who shot kristene chapa and her girlfriend mollie olgin. after police spoke with melchor, they turned their attention to his former roommate, david strickland. police wanted to hear what he had to say and they were not the only ones. here's josh mankiewic