What you should do in a case like this:
1. Demand to see a warrant.
2. If they fail to produce one, have someone in your household call 911 and report that armed gunmen, perporting to be law enforcement officers are attempting to break into your house. State that they are not producing proper identification or authorization, and that for that reason you suspect they are imposters. And tell the 911 operator to tell the responding officers to be careful because you believe these individuals are dangerous.
While they shoot you through the door? You are screwed either way. They know that it will take you money to sue them and several years.