radical cleric al awlaki osama bin laden heir apparent. >> she a strategic hub for getting the message out, in a country with enormous resources. >> reporter: if anyone knows, it is al awlaki. born in america, he spent teen years in yemen and returned to the u.s. at the age of 19 to study engineering at colorado state university. studying engineering, he soon realized a talent for preaching at a mosque near campus. >> he gave a few sermons. it was a long time ago, but they were really good. >> reporter: good enough that without any formal training, al awlaki found himself preaching at the denver islamic society. he began recording cds on islam and the proof at thes.