By the way OP, I don't follow the news and thus don't know anything about what happened. Perhaps linking to a source to the incident you're referencing would help ignoramusses like me (derp) understand things better without having to google-ize it.
A short summary on what went down.
1. Four Americans crossed the border and went into Mexico for a medical procedure
2. They were shot at and later kidnapped
3. Unfortunately, two died.
4. The Cartel, knowing the shit storm they’re about to come under quickly condemned and disowned the actions of the perps, forwarded an apology letter along with the guys who were responsible.
Here’s a link to an article.
https://www.nbcnews.com/news/us-news/gulf-cartel-apologizes-americans-are-kidnapped-killed-mexico-rcna74242