Coonstripe Shrimp

Sold live and by the pound, averaging between 30-40 shrimp per pound. 

How do I "dispatch" them?

Unless you're a highly skilled chef, the best option is to place them in your freezer for 30-60 minutes. Place them in the coldest part and ensure that they get adequate airflow and aren't too crowded together. Because of how small they are trying to use a knife on them while they're alive is unsafe. Once their freezer time is done de-vein and shell them like any other shrimp or prawn.