You remember yesterdays periscope video of a US sub sinking an Iranian ship off Sri Lanka?

I thought this was propaganda, but find several sources see below) as to what really happened.

So, what do we think about the almighty US sinking a defenceless ship - and watching survivors drown.

@MarkHoltom
I want to preface my question by clearly stating that this was unethical. From a legal perspective, would this be considered a war crime? They were defenseless, but at the same time it was a military target.