and he shoots her. and then he runs out of the garage area. >> you're looking at a guy who's by all accounts kind of a hardened gang banger, living that life. what's in it for him to confess to one more murder when he's already in there doing life without parole? >> i can't speak to all of them. but i can speak to this one. he felt bad about this. and he wanted to make it right. >> killing a pregnant woman bothered him? >> yes. >> killing those other people did not? >> didn't seem to, no. >> reporter: police thought they finally had the story of who killed crystal taylor. but it was a story they couldn't tell in court. not yet, anyway. coming up -- that dynamic duo of sister detectives wasn't done yet. >> cagney and lacey shift their focus to derek. >> we never thought he should get away with it.