Heart broken

Where does the short temper angry flares come from? DH lashed out last night - for no reason. We were having a normal, calm conversation and then BAM! It happened so fast - it was over before you could even register what happened - but it did happen.  I asked him to leave - I told him to leave - he refused.  I said you need to leave for the night - get your head on straight - give us all some space.  He refused. Said he was sorry- as if that was enough and now move on. I don't know if he gets what he did - the man I KNEW would never have behaved that way. Is this ADD or something else?