Details Emerge of Seconds Leading Up to Metro-North Crash

PHOTO: Emergency personnel stand near the site of a collision between a Metro-North Railroad train and a SUV in Valhalla, N.Y., Feb. 4, 2015.PlaySeth Wenig/AP Photo
WATCH Final Moments Before the Fatal Metro-North Crash

The engineer of the Metro-North train that crashed into an SUV earlier this week told investigators he saw the car moving onto the tracks seconds before impact.

The National Transportation Safety Board concluded their first full day investigating the crash that left six dead, including the driver of the SUV and five passengers on the train.

NTSB vice chairman Robert Sumwalt said that they have not yet spoken to the train conductor. The engineer, who was interviewed today, said he activated the emergency brake, which prompted the horn to sound for four seconds before the train hit the Mercedes SUV.

The train was travelling at 58 miles per hour - just shy of the area's 60 m.p.h. limit - and took 950 feet to stop.

Officials today examined physical evidence at the scene and units that recorded train and car signals -- but they say they can't get away from a question at the core of the case: Why would an SUV driver pull forward into the path of an oncoming train?

"We're going to do everything we can to try and understand that key fact: Why was that car stopped on the tracks?" National Transportation Safety Board vice chairman Robert Sumwalt said today.

A motorist who said he was in the car behind Ellen Brody, 49, a mother of three, told ABC News after Tuesday's accident that he even backed up to allow Brody to get out of harm's way.

"I’m waiting for her to back up and she moves forward," Rick Hope said. "And she moves forward probably 15 feet right in front of the train. She looked very calm and she took what I thought was an awful long time because I’m thinking the clock is ticking here. The lights are flashing, the gate’s down, you don’t have much time. And I didn’t know what to do. I indicated that I was backing up ... but she looked at me -- I know she did. She got in and all I can imagine is she was trying to make it to the other side."

Metro-North train service resumed this morning at the site of Tuesday’s deadly collision that killed Brody and five passengers.

Service had been shut down in the area around the crash site, which happened near Valhalla on the service’s Harlem Line.

Some 400 feet of the electrified third rail sliced through the train’s first car following the collision, burning the interior of the car and killing five passengers, Sumwalt said Wednesday.

Brody's Mercedes SUV was "pushed about 1,000 feet down the tracks" and "during that time, the third rail penetrated" the first passenger cabin of the train, NTSB vice chairman Robert Sumwalt said. The third rail, which supplies power to the train, began breaking apart in 80-foot segments that started to pile up in the first cabin, but a section also went into the second car as well.

PHOTO: This photo posted to Flickr by the National Transportation Safety Board shows the damaged train involved in a Metro-North accident at a maintenance facility to be further examined, Feb. 4, 2015.National Transportation Safety Board
This photo posted to Flickr by the National Transportation Safety Board shows the damaged train involved in a Metro-North accident at a maintenance facility to be further examined, Feb. 4, 2015.

Sumwalt said that the crash caused a fire and explosion, and "initial indications are that the fire was fueled by gasoline from the SUV." It was not immediately clear how long the power stayed on when the rail entered the train car, but the NTSB said the rail is designed to deactivate if it is separated.

Sumwalt said that NTSB investigators will likely stay in the area for five to seven days collecting witness testimony and what he classified as "perishable" evidence, meaning information that may disappear or disintegrate over time. They have already downloaded the recorders that are in place on the tracks and are calling on witnesses to come forward and share any information they have about the fatal crash.

PHOTO: In this photo posted to Flickr by the National Transportation Safety Board, an inspector examines inside a burned unit from the Metro-North accident.National Transportation Safety Board
In this photo posted to Flickr by the National Transportation Safety Board, an inspector examines inside a burned unit from the Metro-North accident.

Co-workers identified the driver of the SUV as Ellen Brody, a mother of three from Edgemont, New York. Among the dead on the train were Joseph Nadol, 42, of Ossining, New York, Robert Dirks, 36, of Chappaqua, New York, Walter Liedtke, 69, and Eric Vandercar, 53, of Bedford Hills, New York, and Aditya Tomar, 41, of Danbury, Connecticut.

Westchester County Executive Rob Astorino, speaking Wednesday, said that all but one of those killed were charred beyond recognition.

“That train had so many flames in it, it was so engulfed, the inside of that first car is just melted and charred," Astorino said.

PHOTO: This photo posted to Flickr by the National Transportation Safety Board shows the damaged train involved in a Metro-North accident at a maintenance facility to be further examined, Feb. 4, 2015.National Transportation Safety Board
This photo posted to Flickr by the National Transportation Safety Board shows the damaged train involved in a Metro-North accident at a maintenance facility to be further examined, Feb. 4, 2015.

Relatives of the victims were shaken by the tragedy. Brody’s husband, Alan, reflected about his wife’s death in a Facebook post.

“Thank you to those who shared their condolences for the terrible tragedy that took my beloved wife, Ellen,” he wrote.

The Associated Press contributed to this report.

Get real-time updates as this story unfolds. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here.