Southworth also said the operator knew that there were people ahead on the tracks. From the Los Angeles Times:

He said the trainee operator, whom the NTSB interviewed Monday, had sounded the air horn before the accident. The train was moving at 60 mph to 70 mph when it made an emergency stop, Southworth said. He said the operator had heard a radio report warning of workers on the track.

“He was aware of people on the tracks,” Southworth said.

The agency conducted employee interviews today and will interview management tomorrow. It will also schedule a reenactment of the incident.

Update, 3 p.m., Monday: The Contra Costa County coroner has released the names of two people who were killed on Saturday after being struck by a BART train: Laurence Daniels, 66, from Fair Oaks, and Christopher Sheppard, 58, from Hayward. Bay City News reports that Daniels was a contractor working with BART and that Sheppard was a member of American Federation of State, County and Municipal Employees Local 3993. That union is not striking, and BCN says it represents about 210 BART employees, mostly middle managers.

Update, 9:45 p.m.: BART union members held candlelight vigils in Walnut Creek and Oakland this evening to remember two workers who died Saturday when they were struck by a train while working trackside. Alex Emslie covered the Walnut Creek gathering and talked to some of the BART workers in attendance: Fannie Pettis said she knew one of the workers who died Saturday and says BART managers should have ensured the safety of her friend. "I am very angry because I just feel like we should have rules in place to protect our employees at all times regardless of who they are, what they’re doing, and obviously something went wrong," Pettis said Richard Stingily said Saturday's accident shows why unions have tried to highlight safety issues in their contract negotiations. "The safety rules, and the work rules, are very important" Stingily said. "That is one of the most important things here. And situations like this is what we were talking about." Saturday, BART General Manager Grace Crunican and Assistant General Manager Paul Oversier extended their condolences to the families of the victims. When asked whether the accident highlighted the safety issues unions have raised, Oversier said "I'm not going to go there right now." He said sorting out how the accident happened and helping the victims' families was foremost in his mind. "We're dealing with a situation here where the labor issues, the negotiations, are not in the forefront of our mind. We've just lost two members of the BART family." The two people who died Saturday were the seventh and eighth workers to die on the job in BART's 41-year history and the first since 2008.

Update, 5:15 p.m. Sunday: National Transportation Safety Board investigators have taken over the investigation of the accident that killed two workers along BART tracks in Walnut Creek on Saturday afternoon. An NTSB team arrived on the scene of the incident, in which a four-car train operated by a BART manager struck the workers early Sunday afternoon. The victims, one BART employee and one contract worker, were inspecting tracks between the Walnut Creek and Pleasant Hill stations. Jim Southworth, the NTSB's chief railroad accident investigator, is leading the inquiry. He said during a press conference in Walnut Creek this afternoon that only a limited amount of data was available from the train involved in the accident — not as much, say, as would be available from a freight train. Southworth said the train was not equipped with a forward-facing camera that might have captured the scene on the tracks as the accident unfolded. He added that the lead car did have an inward-facing camera in the cab that could shed light on the operator's actions. Southworth said his team could be in the East Bay from four to 10 days and that the investigation could take six to 12 months or more before it's final. "We are at the very start of this investigation," Southworth said. "These accidents occur in an instant but they take a great deal of time to investigate." He declined to speculate on any aspect of the incident, including whether the strike played a role or whether the two workers killed were currently certified to work along the tracks. Southworth said BART, the California Public Utilities Commission, the Federal Transit Administration and the federal Occupational Safety and Health Administration are all participating in the investigation. Update, 5:15 p.m. Saturday: One of the questions that will arise in the aftermath of today's fatal accident: the credentials of the train operator. BART's statement calls the as-yet-unnamed person driving the train "an experienced operator." Contra Costa Times cites sourcesas saying the driver was "an operator supervisor who drove trains two decades ago." The Times also notes that BART General Manager Grace Crunican visited the site of the accident: "Our hearts and prayers go out to the families of the two workers killed on the BART track," she said. Amalgamated Transit Union Local 1555 tweeted in the aftermath of the deaths:

Due to the recent tragedy at Walnut creek station, and out of respect for the families involved ATU's members will not be picketing tomorrow — BART ATU LOCAL 1555 (@ATU_1555) October 19, 2013

Update, 4:20 p.m. Saturday: BART just posted this statementon the accident:

BART officials are responding to the scene of a fatal accident involving two employees who were struck by an out-of-service BART train. The names of the deceased are not being released at this time.The accident occurred at approximately 1:53 pm between the Walnut Creek and Pleasant Hill stations, approximately one mile north of the Walnut Creek Station. The employees were performing track inspections in response to a report of a dip in the track at the time of the accident. The deceased include one BART employee and a contractor. Both people had extensive experience working around moving trains in both the freight train and the rapid transit industry. The procedures involved in track maintenance require one employee to inspect the track and the other to act as a lookout and notify of any oncoming traffic. The train was on a routine maintenance run with an experienced operator at the controls. At the time of the accident the train was being run in automatic mode under computer control. No further details are available at the moment. Updates will be provided as they become available.

Update, 3:55 p.m. Saturday: Audio of BART radio traffic from the time of the incident has been posted online:

AUDIO: BART radio transmission from the moment a maintenance train struck employees on track (warning: graphic) - http://t.co/tJMRcDCANN — Matthew Keys (@MatthewKeysLive) October 19, 2013

Update, 3:50 p.m. Saturday:BART has confirmed a train struck and killed two employees working along the system's tracks between Walnut Creek and Pleasant Hill. The Contra Costa Times reports:

Two BART employees were hit and killed by one of the transit agency's trains between the Walnut Creek and Pleasant Hill stations Saturday afternoon, a BART police deputy chief confirmed. Sources say the two dead workers were non-union engineers performing track inspections when a manager operating a four-car train hit them. ... ... A BART employee, who wished to remain anonymous due to the ongoing strike, said he was monitoring BART transmissions when he heard a manager who was operating a train report an emergency. He said the manager reported that two unrepresented engineers who were performing track maintenance were hit. BART trains have not been running for commuters since Friday due to a labor strike, however some managers have moved trains for other purposes.

The San Francisco Chronicle adds:

The two workers, whose names weren't immediately released, died at the scene after they were hit by an eastbound train, sources close to the investigation said.

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