Won’t work. Unfortunately.
Aggravated assault, or whatever the term is in the state in question, is probably the maximum that will work.
Atempted murder requires that the prosecutor prove to the jury that the attacker(s) intended to kill. And that just doesn’t seem to be the story in most of these cases. The goal appears to mostly indeed be to knock the victim down/out. There’s a considerable jump from that to intending to kill, and being able to prove that beyond a reasonable doubt.
That said, I hope they prosecute all participants, especially those taping or photographing such attacks, to the max allowed by law. And change the law if needed.
It would seem to me that if it were common knowledge among a large percentage of members of a group with the perpetrator that it was not uncommon for victims to die, and there have been deaths, premeditated murder would be a possible charge. They knew their actions had resulted in death but they did it anyway. Not too much of a stretch if you ask me. Viewing from the other side; suicide bombers probably know there were instances where the device detonated with no one except the carrier dying but they went ahead with their task.
they could go for manslaughter/3rd degree murder.