Guess What, each of these have a weakness.
Police can take way too long to arrive, so you may end up with your family possibly done for, and once the police arrive, the serial killer is still out there, since it has now ran away.
Running away you literally become worse than the serial killer, because you left your family to die by the serial killer.
And defending, if you had a good weapon you could get rid of the serial killer, but you must be cautious and careful about this since who knows, the serial killer could be highly trained to knock you out even if you had a shotgun or a rifle.