That’s all true, but just a minor point: “monsignor” is a mis-translation of the Spanish or possibly Italian original, where monseñor is the title used when addressing or speaking about a bishop. So these are bishops, actually, the Colombian bishops’ conference, apparently.
That said, if they chose the latae sententiae route, essentially saying he has automatically excommunicated himself, that means that they didn’t want to do a formal excommunication, probably because they knew there simply weren’t grounds for it. Cowardly weasels, in other words.
For what it’s worth, there is no “Bishop Pedro Mercado” listed on the Church Hierarchy website.
http://www.catholic-hierarchy.org/bishop/llm2.html