To be clear, the news organizations haven’t rejected the claim that the freelance photographers they worked with were complicit in the attacks. They’ve just rejected the claim that they (the news organizations) were complicit, and have cut ties with the photographers who are alleged to be complicit.
Some of the freelance photographers appear to have accompanied Hamas members on attacks on civilians, in a way that implies that they knew the attack was going to happen and were able to prepare to cover it.