In 1920 an anarchist group set off a wagon load of dynamite in front of the New York Stock Exchange at noon on a workday. About 100 people were killed, all workers (clerks, delivery people, secretaries, etc.). Not a single stock broker got a scratch.
The Stock Exchange was, and is, one of capitalism's main roosts, but then, as now, terrorism shows itself to be a reactionary, anti-working class ideology and practice, that stems from a complete lack of willingness to work with the working class, displays a total condescension and mistrust of the working class, does not damage the ruling class or their apparatus, but, in fact, only gives them the excuse to clamp down harder on working people and sincere activists and revolutionaries.
One of the leaflets circulating says that "terrorism as a tactic for fighting back has always been a loser". The leaflet is very good, but this particular line reads as if terrorism is just a misguided tactic against a common enemy.
Terrorism by its nature is against the working class, and there is no better example than the case of the World Trade Center. With their planning and resources they could have killed more workers, but they could have killed less, also.
If the idea was only to destroy a symbol of capitalism or to show their power they could just as easily have hit the buildings at night when they were unoccupied, blown up the Statue of Liberty, the Brooklyn Bridge, hit the Capitol, whatever. Clearly mass deaths was part of the intent, and part of the plan.