I observed people making posts including specific technical details of the firearms used (like magazine capacity and rate of fire), and when pressed to explain

I observed people making posts including specific technical details of the firearms used (like magazine capacity and rate of fire), and when pressed to explain where they got the numbers since they were unrealistically high, they admitted that it was all inferred from a few brief video clips. Unless it turns out that the shooter was using a literal belt-fed machine gun (and one with an impressively high rate of fire at that), people were simply drawing dumb conclusions from the raw footage and some headlines because they assumed it painted a complete picture. That's not a fake news problem, but it is a problem.