Rationality is one thing. Internal coherence is another. This was not even crazy logic. Example of Crazy Logic: This two year old child is part of a conspiracy. I know because of the way his mother looked at me. So now that I’ve kidnapped him, I must sacrifice him to Baal. That is internally coherent. It’s just crazy.
The whistling and the chanting, and killing one and letting one live, however, is just arbitrary mishigas.
It could depend on how much they had “looted”, or whether one of them belonged to a “friendly” family/clan, or whether one of the shooters just felt like killing that day, or.....
This is a mob we are talking about, most of them with low IQ and lots of testosterone. Things happen.....