When it's me, and I catch myself in similar behavior, i know precisely why. I don't know why at the time but 5 or 10 minutes later it hits me like a ton of bricks - a fair amount of time and practice in recovery keeps me wise to the games my mind likes to play.
In MY case, it's ALWAYS been because I'm not "at ease" in one or several areas of my life. The unmanagability there is leading to frustration and that frustration, while small at the time, builds and builds. Add in some "lack of power" in areas where I'm convinced I "should" have power and my angst rises even faster. Over time, the pressure builds - almost imperceptibly as it's happening - but unless something changes within me....... you can bet money on SOMEONE paying the price. Sooner or later, I'm going to make someone pay for my discomfort.
The tough parts were always that I didn't even notice the "pressure" building in the first place and I didn't become aware of it until after I'd just unloaded on someone. The good news for you Dog is that you didn't get that far. If it were me, I know the problem, or the "reason," is absolutely inside me - the way I've been thinking, perceiving and/or acting lately. When what I'm doing gets out of line with the spiritual way of living that I try and maintain, I get wound up and the end result is usually me taking it out on someone else...... or at least wanting to reeeeeeally bad.