Not the most obvious HN subject matter, but I thought the data-driven approach of this article offered worthwhile perspective on an issue that impacts the quality of life for the many HN readers based in the US.
tl;dr: On average, every 22hr or so, someone somewhere in the US "goes postal" and manages to kill at least four other people.
As the article points out, the Mass Shooting Tracker tracks mass shootings (at least four people shot), not mass murders.