Foursquare's Dennis Crowley Tweets From Scene of Boston Marathon Explosions

Dennis Crowley, the CEO and co-founder of Foursquare, ran in Monday's Boston Marathon, but emerged unhurt after explosions marred the event. Crowley used Twitter to report from the scene of the incident.
Crowley, who also used Foursquare to check in at every mile, sent his first tweet at 3:08 EDT.