'Coming of age'? SPOILERS

PLOT SPOILERS FOLLOWING

This has been described as a "coming of age" type film - the boy "matures" in his attitudes about his family and the world, while losing his father and making big decisions, etc.
But is needlessly murdering his uncle by shooting him in the back also a part of "coming of age"?
His uncle was some kind of "collaborator", and I guess part of the boy's "coming of age" is his realising and evaluating the subtle differences between types of "collaboration/resistance" in his father and uncle. But is the uncle's collaboration used to justify the boy murdering him in cold blood (ie. not in self-defence, more out of "childish" anger than anything)?
Is this sort of senseless violence being accepted/promoted as part of "coming of age" for a normal person? (Or have I missed plot elements showing the uncle to be a threat to the boy, his family, or the airman's escape attempt?)

I'd be genuinely interested in comments, since it left me a bit confused as to what to think about the filmmakers' intentions/attitudes.