This answers all the questions but why.
For example is this soldiers initiative or part of a general tactics encouraged by the higher command?
Was the execution justified (i.e. motivated, that is, it was not a cover up or a random killing)?
I can come up with few reasons to kill the woman but why the child? Is there some message behind this killing?
Naturally these questions do not matter for despising such behaviour but are important to help to understand the human nature.
It's something I'd really like to know, after reading through this. I don't understand anything but the most superficial issues facing this region, and it rather shocked me that the national military that's up there to quell the Boko Haram insurgency is committing these atrocities.
I mean, yes, people kill people for fun. People kill children because they're monsters, and I get that. But is that what's happening here? Or is this ethnic cleansing? Or is this something else entirely?
Anyway, it's clarified as motivated.
i.e. what was the murderer's justification or motivation.
I always believe that understanding is important. There are those who think "Understanding==Condoning", which I find a tremendously, and needlessly, false equivalency. I think you need to understand, to trully fight and hopefully defeat something.
How far does the atrocity go? What are the causes? Is this a one-of or repeated act? Who all is involved? And, ultimately, What are the inflection points that can lead to effective prevention?
"It is the mark of an educated mind to be able to entertain a thought without accepting it."
If you demonize and dehumanize your ideological opponents - and even true enemies - you won't be able to understand them well enough to effectively counter them.
For the particular case it might not but for general reaction it does.