let's get right to julie loncich live in braintree with the latest tonight. julie? >> reporter: that they said is really the only focus of their investigation right now, operator error. meantime passengers say this train was traveling perhaps 40 to 60 miles per hour at its peak and they were all wondering why it wasn't stopping. >> we failed our passengers today. >> reporter: for nine harrowing minutes 50 passengers were on a run-away red line >> all the lights went off, so everything was dark. we had no lights in the entire cars. >> that's the first time i noticed in quincy center we were going really fast and i was like wow, that's really weird. we hadn't stopped. >> reporter: the 6 a.m. train left braintree and barreled through four stops before finally coming to a stop between north quincy and js umass all without an operator. david vazquez had been cleared to put the train in bypass mode because of a broken signal. he was supposed to engage two brake systems and throw a toggle...