In 1984, a CFA Executive was about to meet with an arms dealer for a potential meet regarding the sale of weapons. His higher ups in the CFA wanted them to continue fighting, which he ultimately allowed, although it is implied he didn't like the deal.
Diamond Dogs quickly got wind of this and were hired to take him out. They also suspected that the CFA was under the employ of XOF, due to the various PFs having Skull Face's fingerprints all over their presence.
Behind the scenes
The CFA Executive is one of two key targets in the main mission The War Economy in Metal Gear Solid V: The Phantom Pain. The player can either assassinate him or extract him. If they chose to do the latter, Miller will give a debriefing where he explains what happened back there from what the CFA executive reported, and that the latter wished to join them.