New York City —The driver of a New York commuter train that derailed on Sunday, December 1, killing four people, told federal investigators he “zoned out” shortly before the crash, the driver’s labor union leader said.

The seven-car train was traveling at 82 miles per hour (132 km per hour), nearly threeDriver in fatal New York train crash says he ‘zoned out’ times the speed limit for the curved section of track where it crashed, investigators have said. The driver, William Rockefeller, 46, applied the brakes five seconds before it derailed.

The crash also critically injured 11 people and snarled travel for the roughly 26,000 regular commuters on the Metro-North Hudson line that serves suburbs north of New York City.

On Tuesday, December 3, Rockefeller told National Transportation Safety Board investigators that “he nodded. He zoned out,” Anthony Bottalico, the general chairman of the driver’s labor union, the Association of Commuter Rail Employees, said.

Rockefeller told investigators that “by the time he realized (what was happening) it was almost into the curve,” Bottalico said. “He put the train into neutral and put the brakes on immediately. That’s what he acknowledged he did.”

The NTSB has cautioned that its investigation would continue for weeks, if not months, and it was far from reaching a conclusion on the cause.

Alcohol tests on Rockefeller came back negative, NTSB member Earl Weener told a news conference on Tuesday, adding the results of drug tests were still pending.