Tesla CEO says he's working on another secret 'masterplan'

Tesla Motors CEO Elon Musk, under pressure after a fatal crash involving one of his electric cars, went on Twitter Sunday to say he's working on another "Top Secret Tesla Masterplan."

The tantalizing message echoes an August 2006 blog post, titled "The Secret Tesla Motors Master Plan (just between you and me)," in which Musk unveiled the cars that became the Tesla Model S four-door family car and the Tesla 3 sports sedan.