I can think of a single example in my living memory within the US, the loner who attacked the congressional softball game was left of the average democrat. How much farther left, I don’t recall.

Part of that surely has to do with the way the gun debate in this country has been framed, and the positions the left has taken up on the same. That’s a separate conversation, of course, but I hypothesize that the dearth of guns on the left also leads to a dearth of acts that kill people. Well, that, and the lack of baseless bs conspiracy theories (mostly).

Edit: Source