Massad Ayoob of the Massad Ayoob Group demonstrates the gold standard for how to run the Tueller Drill.
This is run in a shooting class, but it’s useful across all disciplines for showing how far away someone can be and still pose a serious threat with a contact weapon.
Note: the Tueller Drill is up there with Col. Boyd’s OODA model on the list of things that are catastrophically misunderstood in the defensive training community. (For example, there is no such thing as a “21 foot rule”.)
Check out the original source, which is Dennis Tueller’s How Close Is Too Close? article in SWAT Magazine.
Gila Hayes did a follow-up interview with Tueller called The Tueller Drill Revisited in the journal of the Armed Citizens’ Legal Defense Network. (ACLDN and their journal are great resources, check them out.)
What about the MythBusters test of the “21 foot rule”? There were some problems. Richard Johnson breaks it down at Blue Sheepdog.