Character mistake: When Frank is starting to show Amy how to take the gun from him he removes the magazine and makes the statement "clip empty" - any Marine, certainly one as well trained as him would never refer to that as a "clip" - it is a magazine. A "clip" is a device intended to help rapidly load ammunition into a magazine.
One Bad Day - S2-E7
Character mistake: The robbers are all trained, they practice, they wear masks...and none of them wear gloves, despite all being ex-military so their fingerprints will be easily traceable.
Answer: He calls him back.