diagram that we received in the mail. >> this is the sheet of paper detective ruiz found. you can see the indentations of the bolt threads in the middle of the page about a third of the way down. and here's that same sheet of paper enhanced by the atf crime lab. and here is the original bomb diagram mailed to investigators back in august. >> the most amazing thing in the world. this is the smoking gun. >> unbelievable. couldn't believe it. exciting doesn't begin to describe. elated maybe. >> then what happens? >> i went out and arrested paul moore. coming up, pete moore seems to be in the clear, but he's got yet another shock in store. >> there's no scale for this. this changes you forever. >> when "dateline" continues. >> when "dateline" continues