Authorities have begun their investigation into Sunday's Metro-North train crash that left four people dead and at least 60 injured. In what one firefighter described to the New York Post as a "bloodbath," three of the victims' bodies were ejected from the train, which was traveling at excessive speeds as it rounded a bend under the Henry Hudson Bridge in the Bronx.

According to the New York Times, the train's operator, William Rockefeller, 46, a 14-year MTA veteran, told emergency responders that the brakes failed, and he performed an emergency maneuver—called "dumping" the brakes, or pulling the emergency brakes on all eight cars simultaneously—in order to slow the train, which was carrying about 150 passengers.

The locomotive and all seven passenger cars derailed, sending several cars near the bank of the Hudson River and ejecting three passengers, all of whom were killed.

"[The victim] seemed like she had lost most of her head. The side of the car was just covered in her blood," passenger Emili Miyauchi told the New York Post of one of the dead passengers, adding that she covered the body with her yoga mat.

Two men and two women were killed: James Lovell, 58, a father of four from Cold Spring, New York; Ahn Kisook, 35, a nurse from Queens; James Ferrari, 59, from Westchester County, New York, and Donna Smith, 54, a paralegal from Newburgh.

The investigation into the crash will likely take weeks, and the National Transportation Safety Board has sent officials to help inspect the crash site and listen to the trains "event recorders," which are similar to flight recorders on airplanes.

But at least one official close to the investigation told the New York Daily News that human error was to blame. "It's definitely human error," the source said. "The speed was excessive."

As bad as it was, the crash would have been significantly worse if it hadn't occurred early Sunday morning. "On a work day, fully occupied, it would have been a tremendous disaster," New York City Fire Commissioner Salvatore J. Cassano said.

[Image via AP]