A writer may indeed have to think like a terrorist, though obviously for different reasons. Both the writer and the killer has to think up a scenario which will attract the attention--and perhaps stoke the fear--of the public at large. Shooting a random gas station attendant certainly won't long capture the attention of a public jaded towards such "routine" violence just as an action film about such a subject wouldn't be very interesting. If I'm not mistaken even the scenario of using airplanes to ram public buildings appeared in literature prior to the 9/11/01 attacks.
J_A_B