Terrorism is in general a method of political control. It started with the Reign of Terror in France. It was used by the Bolsheviks  as a means to establish their authority. The basic idea was explained by Trotsky: if there is a reason for the arrests in the middle of the night and the sending of millions to die in the Gulags, then it is not terror. No one is scared if there are reasons. Thus we have Stalin using this idea to control the USSR. He would send orders to many cities in the USSR ordering the local KGB to arrest a certain number of people, to execute another number of people, to jail such and such a number and to send to the Gulag such and such a sum. So there was no reason for the arrests except simply to fill a quota.
Another example is in Israel where Muslims are blowing up shooting and murdering Jews pretty much on a random basis. There is never any particular reason for it except as a means of political protest. I used walk down Jaffa street every day to go the the Western Wall and one day I changed by usually routine  and it just so happened that the day I changed my route and the very time I usually was on Jaffa some Arab had gotten hold of  a sub-machine Gun and mowed down the Jews walking on the opposite side-of the street.[That was the right hand side of the street when you are walking to the Western Wall.]

That is different than taking over an empty Federal building until some grievances are solved.