own brother to his death. when ted was arrested, under the bed where he slept was another bomb wrapped in a package, apparently ready to be mailed to someone. >> reporter: ted kaczynski rejected his attorney's insanity defense and pleaded guilty to murder. he was sentenced to life in prison with no opportunity for parole. but to this day, david believes ted is insane and should be in a mental institution. >> my biggest regret is not to have clearer insight that he was ill. >> reporter: david continues to write to his brother twice a year in prison. he has never received a response. coming up -- >> it looks like a fireball. people let out a scream all around me. >> reporter: keira phillips on