The irritation and fear demonstrated in the prologue at these miniscule things is the director's way of introducing a question. A mysterious blackout occurs, and for reasons nobody understands, it affects phone lines, and all radio and television stations, so there is no communication. Nobody understands what is going on. Rumors travel like spreading brush fires. The social fabric starts to decay.
People start to ignore the normal conventions of society.
There is some looting, some excessive gunplay, some more paranoia. The nights are particularly frightening. People don't trust each other. Because there are some legitimate reasons to be afraid, the fear builds upon itself, and people find more reasons to be afraid and distrustful. Great set up, abetted by spooky and imaginative directorial techniques.