Yes sir, No sir

A man with a gun went into a bank and demanded their money.
Once he was given the money, he turned to a customer and asked, 'Did you see me rob this bank?'
The man replied, 'Yes sir, I did'. The robber then shot him and killed him instantly.
He then turned to a couple standing next to him and asked the woman, 'Did you see me rob this bank?'
The woman replied, 'No sir, but my husband did'.