remember, back in the 19 eighties, mark and marcus busch locked up some tough customers there. >> i wasbout the murder cases that we prosecuted, people who had life sentences, who are starting their pearl out. >> someone who got out of jail, had its grudge where -- >> you've been though investigators were convinced that he was murdered because of his job as a prosecutor, they didn't stop there. >> you still have to interview friends, family members, associates. >> he wasn't married, he didn't have any children. those extensive checks came out empty and his background. >> there was nothing there. he loved his mother, he spent a lot of time with her in dallas, to go out to dinner. >> all of these checks into mark's personal life were not planning out. frustration was sitting in, we because cases become harder to solve after 48 hours. two full days in, mark's murder had reached that crossword road. one >> insiders tell us there is simply no promising leads in this case right now. with this is turning into a real whodunnit? >> will anyone who can give us information on who did this, will be