William Rockefeller Jr., the 46-year-old engineer of the commuter train that crashed in the Bronx Sunday morning, might be responsible for the deadly accident that killed four people and injured more than 70, DNAinfo New York reported, citing unnamed sources.

Rockefeller, who was at the controls of the Metro-North train, was reportedly dozing as the train approached one of the sharpest bends on the line, at a speed of 82 miles per hour. According to the report, Rockefeller “all but admitted he was falling asleep” as the train neared the curved section, in his statements made shortly after the accident.

DNAinfo reported that investigators believe the engineer woke up just as the train entered the curve and attempted to reduce the train’s speed by applying the brakes, but it was too late. 

Rockefeller reportedly claimed that he applied the brakes but the train did not stop due to faulty equipment. The allowed speed on the curve is 30 miles per hour, and on straight stretches the speed limit is set at 70 miles per hour.

Earl Weener, member of the National Transportation Safety Board team that is investigating the accident, said at a press conference on Monday that the brakes were engaged “very late in the game,” only six seconds before the crash, DNAinfo reported.

Rockefeller has been an engineer for about 11 years and a Metro-North employee for 20 years, with an unblemished record.

Rockefeller took drug and alcohol tests after the accident, but investigators believe neither factor caused the mishap, the report said, citing sources, adding that prosecutors had subpoenaed the engineer's cell phone but they did not believe he was using it at the time of the accident.