reporter: and an angry manifesto left behind. here in austin, texas. 53-year-old joe stack made a missile of his small plane. slamming it into an irs office. a final expression of a simmering rage. on the surface, joe stack seemed like a good guy, sound and perfectly sane. so what led this regular joe to become what some would call a domestic terrorist? what drove him to kill on february 18? he was like the poster boy for chill. reporter: rick furly was a band mate of joe stack s. joe played base and was the kind of guy you could count on. superprofessional. reporter: billy eli was the front man who brought stack into the band. he says the joe stack who flew his plane into a building was not the same joe stack he knew. some people call him a domestic terrorist. yeah, some people do. and some people call him all kinds of things, man. i called him a friend of mine and my bass player. i mean i wasn t aware of any political agenda that he ever had. reporter: austin