The National Transportation Safety Board (NTSB) conducted an investigation into the fatal 2014 car crash between a Wal-Mart truck driver and a limo carrying actor and comedian Tracy Morgan. The results of the investigation concluded that driver's fatigue, speeding and failure to wear a seat belt all were contributing factors in the severe accident, reported Reuters.

Truck driver Kevin Roper had driven 800 miles overnight from Georgia to the Wal-Mart distribution center in Delaware and proceeded on his delivery route, NTSB officials said in a public hearing. Roper had been awake for more than 28 hours before the crash, according to the Associated Press.

The delivery truck was travelling 65 miles per hour in a 45 miles per hour work zone near Cranbury, N.J., June 7 when it collided with the rear-end of a limousine carrying Morgan, Morgan's mentor and comedian James "Jimmy Mack" McNair and other passengers who were traveling back from a show in Delaware. Morgan,the 46-year-old "30 Rock" and "Saturday Night Live" star, suffered serious brain trauma and remained in a coma for two weeks following the accident. McNair, 62, was killed in the collision.

Morgan settled with Wal-Mart under undisclosed terms, and the company has been devoted to improving fatigue management programs for its drivers and dispatchers, reported the New York Times. Investigators determined Roper's fatigue "made him slow to react" during the incident.

Six cars were involved in the collision and 21 people were affected, nine of which reported injuries.

Roper's lawyer, Philadelphia attorney David Glassman, disputed the claim that his client had been awake for 28 hours at the time of the accident.

"Not only are we disputing it," Glassman told the AP, "it is factually wrong."