In the case of the pizza guy, it was reported that he was working with others to rob the bank and their plans went wrong. I believe the others were caught and convicted.
I looked at the wikipedia on the case. They determined he was involved in the plot based on the plea bargain testimony of one of the participants. And the prosecutor never did try to establish what was “in it” for the guy with the bomb on his neck.
And if he was NOT involved in the plot, then the police would have a “wrongful death” case on their hand because he died with a bomb on his neck that they did nothing to defuse (he sat there for 30 minutes with time ticking only to die right as the bomb squad arrived).
I suspect it is like the anthrax attacks that they were certain were the work of one professor and then were certain were the work of a different professor.
Clear the books and just forget about it.