No. This is bullshit. I am telling you, from personal experience, that there are claims in this article that are completely bullshit, and stand out as being completely bullshit. Whoever this "journalist" is writing about has sold Buzzfeed quite a cool story, bro. I'm not doubting that assassinations are carried out by mercenaries, which is not even a little bit unusual historically. I only skimmed the last third of the article because it's such outlandishly bad and wholly unbelievable storytelling. And as someone that spent more than a couple of years looking at the universe through black hot thermal, something about that footage is not quite right. I could spend hours unraveling the tall tale Buzzfeed has spun here for you all today. Just a few of the claims that are outright false or smack heavily of exaggerated bullshit:

"... the US doesn’t ban mercenaries. And with some exceptions, it is perfectly legal to serve in foreign militaries, whether one is motivated by idealism or money. With no legal consequences ..." False. Totally false. You jeopardize your American citizenship by serving in a foreign military ranked as an NCO or above. It is the exception to do this without huge problems and not the norm. For example serving in the IDF as part of your Return. I know because I personally had an offer to join an allied European military in order to take a teaching position at their infantry school. And the US government is putting people in jail that went to fight in Syria and Iraq with e.g. PKK.

"If the [reserve special forces] soldiers are not on active duty, he added, they are not obligated to report what they’re doing." 100% false. You need a waiver signed by your chain of command (up through battalion commander) to do anything remotely like this, which would absolutely need to be approved, taking security contractor work like this, overseas. You absolutely are obligated not just to report to your chain of command but to get a waiver. I know because I personally have friends that did contracting work while in the guard, and I know the hoops they had to jump through.

"During a live-fire training mission he led, back in his Navy days, he says he accidentally shot another SEAL." You couldn't "choose to leave the Navy" after that. This would be a huge fucking problem. Probably a discharge. Possibly jail time.

"the number of special operations forces has more than doubled since 9/11, from 33,000 to 70,000. That’s a vast pool of crack soldiers selected, trained, and combat-tested by the most elite units of the US military" Seventy thousand maybe if you include all of the REMF POGs doing paperwork, but nobody could reasonably call these people "crack soldiers" and compare them to an 18B.

It looks like Buzzfeed as been Buzzfed. Somebody sold them a story that is almost certainly equal parts unbelievable exaggeration and complete and total bullshit. And even if the footage is real -- and I do not believe it is 100% genuine -- they're deliberately zooming in on the area where the "mercenary" is firing his weapon in order to obscure what appear to be rounds landing at his feet. It looks like he's provoked into firing. Do not believe anything these people are telling you. It is almost certainly invented for clicks or some other reason.