The word may will be used for any evidence that is not strong as said UNRWA employees bursting into the OIOS armed with guns, marked with Hamas headband and shouting slogans.
Even if they have pay slips from Hamas or video evidence they will use the word may.
It's a common usage in formal text. But don't trust me, open scientific papers from high impact journals. You will find the word 'may' being used in a similar fasion.
As for evidence from Israel, it goes down to he-said. As Israel claims they provided evidence[0]. As both sides have interest to lie, I don't believe any of them.
It will take a lot of time for a clearer picture to emerge. But in the meantime you can collect puzzle pieces by your self. For example, Hamas' announcement on the death of head of operations in Lebanon [1] raised a familiar name! The beloved school manager that UNRWA suspended [2]