Presidential pardons have no impact and their liability for state-law murder charges (though federal seizure of crime scenes and destruction of evidence might, in practice.)

I'll eat your hat if any of these goons ever see in the inside of a holding cell

But pardons only apply to federal crimes… murder is a state offense.

That depends, the civil service has a lot of leverage because most of them cannot easily be fired. And POTUS needs the civil service to execute his policy goals so his fellow party members and possibly himself can get re-elected.

Therefore there is considerable leverage for allied servants to form an alliance that more or less offers their allegiance in exchange for non-prosecution. I would expect especially DHS to basically become a non-functional (or even seditious) department if they prosecute those guys and they could purposefully make the president look bad by making his security apparatus look incompetent.

Maybe not in the most recent case with the border patrol. Aside from their bad gear and bad communication the agent that cleared the Sig said "Muffled word Gun" and the guys holding the known agitator down clearly misunderstood that as "Gun!" so they repeated it and the agent in cover position fired. I'm sure it did not help that all these guys could hear is blaring loud whistles which is why I would personally hold the protestors partially responsible. I know I will catch flak for those observations but I stand by them as I am neither left nor right and these observations are just obvious. As an insufferable principal armchair commander I would also add that these incidents are primarily occurring in sanctuary cities where antifa community organizers are escalating non stop in hopes that someone dies and they can use it as political fodder later on and in hopes they can radicalize people. Just my opinion but I think it is going to backfire. The normies can see what is going on.