Setup: there's a bomb in a coffee shop. Suspense: they don't know it's there.

Classic Hitchcock, but this is the present. The insecure cameras allow the bomb to recognize faces, and thence names. It won't explode until the right person walks in.

Face recognition not being perfect, there is more than one bomb. Homeland Defense only figures things out after the third explosion.

As they don't know how many bombs there are, or where, the city expels everybody with a certain kind of face.

It's not your death, but I'm still satisfied.