After the train hit the vehicle, the third rail supplying electricity to the train broke, penetrated the car and further penetrated the first and then the second train car, Sumwalt said.
An explosion occurred after the impact.
The car driver, a woman, died in the accident, as well as five train passengers. Sumwalt noted it is unusual for people inside the train to get killed during such accident.
“We intend to find out what makes this accident different,” he said. “Two big questions: Why was the car on the train tracks? And what caused this accident to be fatal for occupants of the train.”
Last year 769 people died in almost 11,000 railway accidents in the United States, up from 706 casualties the year before, according to the Federal Railway Administration.
In some 2,000 accidents happening every year on highway-train crossings, 239 people lost their lives last year, up from 231 in 2013.