. >> also known as nick combs. a tough prosecutored determined to find justice for the carrick family. prosecutor combs finds a key witness. his name, shane lamb. >> who is shane lamb? >> shane lamb, he's got a criminal history. he grew up rough. i think he's a very tragic character in all of this. >> a stockboy at val's who worked alongside brian and mario. a five-time felon with a rap sheet that included attempted murder at just 14. he repeatedly denied knowing anything about brian's disappearance to authorities. now eight years later in jail facing up to 12 years on drug charges, he was ready to talk. but first he wanted a deal and >> shane lamb is given immunity from the offense of murder and voluntary homicide. >> with this deal, shane escaped all charges related to brian's death and a reduced drug sentence. all he had to do to get the deal, tell his story. and that led police to mario. >> what exactly did mario tell you? >> pretty much talk to brian, intimidate him into getting the money. >> how were you to in