@deancsmith, a local televisionographer, sent Breaking Tweets this TwitPic of the destroyed RV after the crash:
The San Mateo County Fire Dispatch provided the first tweet on the accident.
One Twitterer was on board another Bay Area train service, Caltrain, and tweeted about unusual delays. He soon learned the reason and provided a feel for being on the tracks.
Twitterers in the area, including journalists, provided additional information.