It's not the first time I've seen such a video involving an off-duty Brazilian cop shooting someone while holding a child. It's quite possible that expectations of them might be different than of ours, or simply a difference in "cop culture" there. The officer indicated he was afraid of what would happen once he identified himself as an officer, so he may have been obligated by the requirements of his job to do so. I find it difficult to believe that such a requirement, if indeed in place, would apply in all situations, but I'm not there and can't say one way or the other. When I was on the job, we did indeed have a "duty to respond", even when off-duty, and each of us was required to have our badge, ID, and firearm at all times while within the city. However, it was written into the policy that unreasonable risk was not required.
As pointed out, there are some factors that would have to be known before I could make such a decision on this particular case. In other words, I would actually have to have been there. Robbers in Brazil seem to be more brazen than many of them here, and there is no guarantee that they'll leave without exacting violence as they do so. Yes, that happens here, too, but it seems less common than there.