The driver of the Metro-North train that derailed Sunday had fallen asleep moments before going around a dangerous curve that required the train to be slowed down to 30 mph, investigators told DNA Info on Tuesday. William Rockefeller, a veteran engineer with an unblemished record, allegedly dozed off for a few fateful moments, and awoke as the train sped around the curve, too late to slow down. Rockefeller, and the rest of the Metro North crew, took drug and alcohol tests, but all came back negative. His cellphone records have also been subpoenaed. Four people were killed in the derailment and at least 60 more were injured.