In recent days, Peters received "substantive information" dealing with the Horan family's dispute, which is understood to have included financial and other records.
As a result, certain things are said to have fallen into place.
For Peters - a stickler for evidence in document form - there seems to have been enough to persuade him that he could no longer have confidence in Horan.
Hence, Horan's expulsion from the caucus by unanimous vote - and inevitable expulsion from the party, something that requires the say-so of the board of NZ First.
Peters was so sure of his ground he did not even read Horan's press release yesterday denying any suggestion he had stolen from his mother or misappropriated her money and assets, and expressing confidence any "proper" investigation would exonerate him entirely.
Horan's expulsion is not without risk for NZ First. As an independent MP, Horan could be a nuisance for Peters and his party - at least temporarily. There will be no longer-term damage to the party from this affair.
Horan says he is going to stay in Parliament. He has no mandate for doing so. He is only there because of Peters' ability to pull votes. Horan should now do the proper thing and resign from Parliament altogether.