MInd searching for what triggered it is the mind believing that if it can figure out what triggered this you will have the power to change or orchestrate his (x's)functioning ... like have control over the other persons head space and trigger system.

What the X is doing is about controlling you and getting your attention. His anger is about him and formerly as in presently he projects his demons on to you. Then he wants to get those demons.

He likely did through out in the marriage. it is an all encompassing program that doesn't change. You did not create that program but you used to be employed there and he needs your employment because likely he can not find an adequate replacement . Mind you he is not looking for a individual or person but an object to render his fears against a.k.a. the best defense is attack.

People who are disordered like NPD aka pathological do not abide by boundaries / target / predatorial. The x's actions are those of a predator.

In order to change this in the future do not share the same people. Get far away from his pool and create the most amount of distance from his paths/people/network.

You are fortunate that the accountant contacted you and did not trust your ex-wife. It is hard to answer what would trigger an ex-spouse to be vindictive. Maybe you should ask your ex-family for more information. My husband's ex was like this. Some people are jealous and mean by nature. My ex also did some mean things. This is not unusual. To give an answer we would need more information about your situation. Even after 25-years my husband's ex was very vindictive. There was a long court battle over money and the kids. Now it is over as she died but her actions had a long-term effect on my husband's relationship with his 4-children. Be glad you divorced her.