If you're referring to the "people who physically killed them" as the individual(s) who operated the drone(s), I imagine they are the ones who need the most (mental) help, after learning their superiors provided faulty intelligence and allegedly killed innocent people.[0]

The two(+) that are perhaps the most relevant are those that provided the intelligence (framing), and those that made the decision to act on it.

[0] I don't know how much liberty drone operators have to make live decisions in the .. "field" about whether to engage or not, but I suspect this case involved some level of abstraction.