As a libertarian I am firmly against violence directed at functionaries of the State, as a strategy or tactic to produce positive change.
This doesn't work (like killing cockroaches with your shoe, there's always many more) and causes a tremendous blowback. Nearly everyone in the US believes in democratic voting for change rather than victory by killing your opponents. Violence can only intimidate, not convince.
This is why the recent anti-Trump/GOP, progressive Democrat shooter in Virginia was totally wrong-headed for his attack. Any similar acts should be condemned regardless of who or why committed.
That is clear.
Nonetheless, it is hard to miss the irony. There is dramatic fuss over the (thus far) nonlethal act by one deranged individual against members of a body which — as a whole — directs millions of armed killers who daily inflict thousands of grievous wounds upon others. Congress tells us we need no obsolete Declaration of War to arm and fund these military killers in dozens of foreign lands. They merely label people as "enemies" and the shooting begins. Let the drones fly!
In Roman imperial times when the Huns, Goths and Vandals arrived at the gates of the capital city, Senators knew trouble was at their door. They either bugged out or coughed up treasure as bribes. They were happy to vote for imperial wars so long as they could stay safe at home and enjoy the spoils. Not so happy when vengeful barbarians wanted payback. Rome was sacked more than once.