>> the '90s bring on a whole new challenge for law enforcement, lone-wolves. >> it really was the proverbial needle in a haystack. >> all authorities have to go on is a composite sketch of a white male believed to be in his 40s. >> he wasn't the only bomber we had investigated before. but his lone solitary operation as a serial bomber was so unique. >> unibomb hotline? >> so far thousands of tips phoned into the san francisco unibomb task force have led nowhere. >> we began an entirely new look at this, an entirely new strategy. we brought in a crew of analysts from fbi headquarters. they worked 24/7, but sadly it happened again. [ siren ] >> a mail bomb explodes inside the california forestry association building. >> the killer known as the unabomber says he will stop mailing package bombs if the newspapers will publish his political theories. >> when we received the manifesto, we felt very strongly