classes and turned over the tape to the fbi. the fbi says that professor s actions proved crucial to their investigation some six years later. on a hunch, la blanc asked agents to show ha video of him to sa save. from that video he was able to make on identification. reporter: on 9/11, his mother, who doesn t want to be named, says he called home for the last time. he called me and said did you hear what happened, so on, so on. they said they put it on the muslims. i said yes. i tell him do not come. and do not come. because the all against the muslim people. he was arguing with me. he say no, i didn t do nothing. i will come. don t worry about it. reporter: his mother adamantly denies her son is directing al qaeda attacks. but when i asked about the admitted times square car bomber, she said this.