That's a sign when the relationship between the two people is going to deteriorate and both parties will later regret it.
The thing is, it always takes two people create a conflict. If you refuse to participate in the drama, if you do not engage, if you walk away, the angry trouble-maker will have no choice but to look someplace else to vent.
Feel the heat rising. Feel the fear. Pause and reflect on it. Smile, say something nice, and get back to work.