Social media tends to jump on details as fast as they come out, which is not great given the so called “fog of war.”
Remember when Reddit ‘found’ the Boston marathon bomber?
No one is going to sue some random internet commenter for libel, and the random person doesn’t have an institutional reputation at stake if they back a story that turns out to be false later on.
In theory, large media orgs do have to worry about those things, though standards have slipped a lot recently.
So even without intentionally lying, social media isn’t the most reliable place for information. There are exceptions (the lab leak theory was widely embraced online when mainstream press was presenting it as an open and shut case initially, for example). But the odds are generally not in social media’s favor about any early information on a topic, whether things like school shootings (very often there’s reports of multiple gunmen when there’s actually just one) or world events.
Also, technically I don’t think anyone is saying it’s Hamas. It’s being attributed to a different group.