The mythical ticking timebomb situation is a nice twist on the philosophy discussion around the observer and runaway train.
From memory it goes something like this:
You're in a cabin with the track-switching equipment beside a railway. You can see in the distance a group of 5 people walking along the track. In the other direction you can see an out of control train. You can switch the tracks so the train will be diverted onto another track, avoiding the people and averting a catastrophe.
Most people switch the track.
But now you introduce a single person on the alternative track. If you do nothing 5 people will die. But if you switch tracks one person will die.
People find this a bit harder to think a out, and are hesitant to say that they'd switch the track.
It seems that if the single person is a TERRORIST that many people would switch the track. They might even switch the track if the single person was a taxi driver that someone else had said was a TERRORIST. They might even switch the track if the single person was an innocent relative of a supposed TERRORIST.