ATLANTA -- Atlanta police said an argument over a $5 T-shirt may have led to a store clerk’s killing.

The clerk was shot Sunday at a Quick Stop convenience store in southwest Atlanta.

Police said the clerk had been behind bulletproof glass, but had stepped out to argue with the gunman.

"As soon as he opened the door, the guy shot him three times in the chest,” said store clerk Zaouder Tour.

Workers said the only witness was a homeless man who helps clean the store.

The gunman tried to shoot the homeless man, workers said, but his clip was empty.