Was DA investigating Sandusky murdered?

>>> we begin this half hour with the penn state child sex abuse scandal. earl whier this week jerry sandusky waived the right to a preliminary hearing tied to that case. today two former penn state officials charged with lying to a grand jury and failing to report sex abuse allegations, face their own day in court and key witness mike mcqueary is expected to testify for the first time in public but there's another mystery in this case, nbc's lester holt has that side of the story. good morning to you.

>> reporter: matt, good morning. it's almost a mystery within a mystery, a story of ray gricar , a pennsylvania district attorney who we now know was the first prosecutor to investigate the allegation of sex abuse with jerry sandusky in 199. we don't know why he chose not to prosecute the case but the bigger mystery and bigger question is why in 2005 did ray gricar suddenly disappear? ray gricar , the d.a. of center county, pennsylvania , had a stellar reputation.

>> he was the most serious prosecutor i've ever met, and i've met hundreds of prosecutors.

>> reporter: by early 2005 , the d.a. was preparing to retire, stepping back from his duties. on april 15th , he decided to play hooky.

>> and he said, "i don't think i'm going to go to work today. i think i'm going to take today off." i said fine, good for you.

>> reporter: that night when his girlfriend, patty fournicola, got home, there was no sign of gricar.

>> to me it was an emergency, this is not like him, it's unusual behavior.

>> reporter: the d.a. was missing. the next day, his red mini cooper was found abandoned 60 miles away in lewisburg, pennsylvania . it smelled of cigarette smoke, there were ash specs on the floor, but the d.a. didn't smoke.

>> ray did not like people smoking around him really and he definitely would never let anybody smoke no his car.

>> reporter: daryl zagani, now retired, was the lead investigator on the case.

>> it would indicate to us somebody who has been in that car smoking or at least was leaning into the car, possibly talking to ray, holding a cigarette, with some of the ash falling to the floor and the smoke getting into the car.

>> reporter: three months later, the d.a.'s work laptop was fished out of the river in lewisburg. its hard drive was hovered soon after, so damaged no data could be retrieved. when you found out that nothing could be recovered, tell me your reaction.

>> very upset. i don't know why. it's like gee, it was like the big carrot hanging there and you reach for it and just about have it, and it's gone.

>> reporter: over time , investigators developed three working theories about the d.a.'s disappearance, that he committed suicide, or walked away, or was murdered. no one knows, and the case remains open. police chief sean weaver now oversees the case. does your department lean in any particular direction?

>> no, actually, we wondon't, and it's hard because we all have our personal thoughts on the case. everyone who has ever looked at the case has their own theory, personal theory, how crazy it mighten.

>> reporter: of course the question folks are asking now, could gricar's disappearance be linked to the sandusky case. close friends and colleagues tell me no way but acknowledged he never really talked about that investigation and matt in tonight's broadcast we'll hear from a prominent medical examiner in pennsylvania who offers his own theory as to how the two could in fact be linked.

>> lester, thank you very much. the broadcast lester is talking about is "dateline" at 10:00 , 9:00 central time here on nbc.