(Psychological / emotional perspective)
Terror in a dream is often the result of unresolved fears and doubts.
It is only by experiencing such a profoundly disturbing emotion that are we likely to make an attempt to confront those fears.
If someone else is terrified in our dream we are in a position to do something about it, and need to work out what course of action should be taken.
The appearance of a terrorist is a negative manifestation of our predisposition to be intensely emotional.