Man robs a bank and takes hostages.

He asks the first hostage if he saw him rob the bank.
The hostage answers, yes.
The robber shoots him dead.

He asks the second hostage if he too saw him rob the bank.  
The second hostage says, yes, and the robber shoots him dead.
The robber goes up to the third hostage and asks him if he saw him rob the bank.
The third hostage answers, "No, but my husband did."