Anger trigerred by other peoples anger

I was lining up at Stima Plaza to pay a bill when this man started a complain. I did not get what had angered him but within no time the complain turned in to a commotion that almost brought the place to still.
I was not on the line he was but of course while in the same hall I would be affected. Little had that been settled than the guy in front of me on the line raised a complain this time to me. "The lady serving us on this line is being too slow!", He said.
I never thought that was the case. The person who had come in at the same time as I on the other line, had the same number of people as I to go before being served. Then it hit me. This guy in front had his anger ignited by the previous commotion. The lady was in no way slower than the rest. That is my lesson today. Be ware of people with 'almost there' tendencies. They can be ignited any time.