I saw fights almost break out between customers a few times when I worked as a cashier before. Mostly, and ironically, it was around the Christmas season when people would have their tensions running high.
It's interesting the article had no pictures.
I'm curious to know if these were two high strung yuppies (the ones I mostly saw who wanted to rip each other's throats out, ironically enough) or if it was a down and dirty ghetto fight.