Here's a statement from the UN Human Rights Office made on one possible mass execution. It states it has confirmed that the killings occurred, and demands an investigation into how they were killed:
https://reliefweb.int/report/occupi...rights-office-opt-unlawful-killings-gaza-city.
From a couple of weeks ago, here is an NGO statement reporting that Palestinians had been detained and later executed, some after their release:
https://reliefweb.int/report/occupi...cting-field-executions-and-mass-killings-enar
Regarding how the IDF would look like to the outside, the exact same word-for-word description could be used to describe militants in Hamas, and for many armies or armed groups, so they're not immune from committing war crimes regardless of how just they believe their cause to be. An average IDF soldier may not be trigger-happy in other times, but after the 7th October and the terrifying rhetoric by those who are running this war, it's pretty easy to see that the sort of environment in which mass executions occur has been entirely enabled.
As I wrote in another post, the IDF have gone far beyond normal conflict red lines and serious voices have warned them they're acting in a manner detrimental to their own interest, and that's why I don't believe that the idea that they just wouldn't commit mass killings 'because it's not something they'd do'. I would've found the idea that the IDF shoots 3 unarmed men waving a white flag who turned out to be hostages to be completely implausible, but it happened. Is it so unbelievable that in this same environment the IDF wouldn't commit mass executions?