This is the train system I take to work everyday. Although this wreck happened on a different line (red) from the one I use (orange). Nine are confirmed dead from a terrible wreck. Apparently an inbound train ran into the back of another train that had stopped. Apparently it was operator error as well as an error in their system. These trains are ran from computers that are supposed to detect when they approach another train that is stopped. Obviously that failed. I don't why the operator didn't manually stop it? We will probably never know the answer that since she was one of the nine killed in accident.
Also if this had been an outbound train this would have been much worse as those trains would have been packed with people heading home for the day.