My gf's bro crossed the finish line 1 minute before this happened. (He's fine, she's not.) Man, humans are just the worst.
Tangential, but related: I was watching BBC a couple weeks ago and they were talking about a bombing in Pakistan. The reporter said an organization "admitted responsibility" for the bombing. I've never been comfortable with the American phrasing of saying an organization "claimed responsibility" for an attack -- as if it could be a point of pride -- and I think the Brits express it better. Anyway...