I agree that an actual vest is unlikely, but there are a lot of backpacks in those videos that won’t get a second look.
Very good point.
If they are willing to escalate to an IED of any sort, they won't care about the "crowds".
Well yes and no, right? Like inherently anyone clacking off explosives doesn't care about crowds, but there is a difference between targets and desired outcomes.
An accelerationist anarchist might pop off a vest because doesn't matter who gets got; the chaos is "the point".
Some ANTIFA/similar person would likely want to target LEOs/Feds more directly, because the hope would be that it galvanizes the protestors left to take up arms. They'd be looking for a martyr moment, which is hard if your victims are mostly your own people.
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Best case scenario is nothing happens and shit cools off before hand, but I'm doubtful it will.