Tonite at Walmart

Was checking out and a man and his wife bring their cart up and start unloading. Cashier as if it was jalapenos and the guy charges over and bends over my stuff to make sure I'm not pulling a fast one when I answered yes.

Thought it was odd and didn't think much of it.

I swipe my card then start loading my cart while the cashier is scanning my items. Turn around he is has his hands doing something on the credit card reader.

I yell "excuse me sir" as I charge him and he runs back behind his wife.

Don't understand what happened, I have never done something like this before.

Guess thought he was stealing but honestly don't know because at the time there was zero thinking involved.

It was scary because I wasn't in control when it happened.

Any one have such a experience?

TL:DR
While loading my cart some guy is trying to steal my card info off the reader.

When I saw him tried to Hulk smash him and he ran and hid behind his wife