In terms of IHL v IHRL:
https://www.amnesty.org/download/Documents/48000/mde150072009en.pdf
Both human rights law and humanitarian are listed under applicable law. There is also considerable literature on whether these are indeed distinct or whether one is a subset of the other but that’s another day’s discussion.
As for their writing on intent. I would like another sentence in a few of their paragraphs. However, as they are stating reasonable grounds of belief, my guess would be the age of some children (11) and the clothing of medical personnel, journalists etc. made it reasonable for them to conclude IDF knew whom they were shooting when they shot those people.
IDF’s response in the tweet suggests a number of alternatives-ricocheted bullets, poor shots, smokescreens and low visibility (personally I find the notion of a chaotic free for all the best defence but the Commission evidently found it was still clear who certain people were when shot.)
Interestingly IDF’s response seemed to be “we don’t intentionally shoot minors or medical personnel of journalists but sometimes the medical personnel are acting suspiciously so we do and sometimes the minors are terrorists so we do.” At least with the journalists they keep up the accidental line (saying they get in the way) but I found the following extract surprising as it appears to break from the “accidental/unintentional” narrative:
With this paragraph in mind I’m not sure questioning “how could they possibly know of intent “ would be my line, as it’s immediately undermined greatly by IDF’s own statement. I’d be more inclined to try and argue those shot were behaving as IDF states above (not that that’s a winning argumemt either in my opinion but at least it’s consistent with the party line).