One of the big ones I remember from the last decade was the Congressional baseball shooting in 2017, where luckily nobody was killed. This isn't a sudden problem to brace for, it's a continuing problem to finally accept and address.
Charlie Kirk was not an elected public official, but he was definitely still political in a way that a lot of regular Americans are political. So even if it's less significant with regard to elected officials being targeted, it was political violence that regular people felt and could conceive of being targeted with, for similar reasons as Charlie. I believe that was what made his assassination resonate with people, much more than an elected official being assassinated does.
Charlie Kirk was not an elected public official, but he was definitely still political in a way that a lot of regular Americans are political. So even if it's less significant with regard to elected officials being targeted, it was political violence that regular people felt and could conceive of being targeted with, for similar reasons as Charlie. I believe that was what made his assassination resonate with people, much more than an elected official being assassinated does.