Much discussion is ensuing about political rhetoric, though there is no knowledge yet of why the shooting took place. I have removed a screen shot of one such an example, at commenter request. For a good discussion, you can follow this link to a Seattle PI, also linked to by a commenter.
Regardless of why the shooting took place, there will be a lot of talk about violence in America in coming days. I hope this more usefully serves as a starting point for that conversation on Swampland.