>> he conducted fragmentation experiments. he conducted explosive mixture experiments, trying to come up with a bomb which would kill effectively. >> and his practice paid off. the bomb he sent to thomas mosser was the deadliest yet. >> authorities say the bomb that killed madison avenue advertising executive thomas mosser was the size of a video cassette tape and was intended for its victim. >> it was loaded with shrapnel. it had green panel nails. when it detonated, it blew with such force, it put a hole in a cast iron skillet. it was just a very devastating explosion. >> behind the casket carrying the body of thomas mosser was the most important part of his life -- his family. >> we were shattered we had lost someone else to the unabomber, and we still hadn't gotten him. >> it's extraordinary that someone like mr. mosser, such a decent human being, is one day alive and living, and the next day, he's not with us. >> it was becoming apparent that this guy wasn't going to stop.