Agreed, we are not prepared for this one, but it has to be carried off perfectly.
Automatic weapons are undeniably the best deterrent to Witnesses.
For extra effect, fire a few rounds into the air or towards their car. Pretend you hear a voice inside your head telling you to kill the witness. Guaranteed to stop future visits for several years. The young couple came to my door. I was wearing my robe, and had just awakened.