A man walked into a bank, produced a gun and demanded all the money.
As he was leaving he asked the next person in the queue "did you see me rob the bank?"
Yes said the man and the robber shot him
The security guard appeared and was asked the same question, gave the same answer and he too was shot.
The only other people in the bank was a man and his mother in law, "did you see me rob the bank?" asked the robber
No said the man but she did.