The National Transportation Safety Board will announce this week that the Metro-North Railroad engineer at the controls last year during a fatal derailment in the Bronx had an undiagnosed sleep disorder, according to a person with knowledge of the planned announcement.

 The engineer, William Rockefeller, suffered from severe sleep apnea, which appeared to be aggravated by a recent change to an early-morning shift shortly before the crash, the person said of the safety board’s findings.

In the days after the derailment, which killed four people and injured more than 70, representatives for Mr. Rockefeller said he appeared to have nodded off as the train raced toward a sharp curve near the Spuyten Duyvil station around 7:20 a.m. on Dec. 1.

Read more at The New York Times.