The accident Saturday morning killed Morgan's comedy writer, James McNair, and sent Morgan to the hospital in critical condition. Three other people were injured in the accident, which included two tractor-trailers and two cars.
Tyrone Gale was driving the limo bus at the time of the accident in New Jersey.
"I climbed around and heard Tracy screaming for help," he said. "I climbed up on the body of the limo bus ... but I couldn't reach them."
"I just remember the impact ... We didn't know which way was up, which way was down. I don't know if we flipped several times or one time," Gale added. "I saw the condition of everybody and I knew it would just make it worse if I tried to pull them up and out of the vehicle."
The injured were taken to Robert Wood Johnson University Hospital, where Morgan was in intensive care. Morgan's assistant Jeff Millea and Ardie Fuqua were both listed in critical condition. Fellow comedian Harris Stanton was treated and released from the hospital.
Law enforcement officials believe the accident was caused by one of the tractor-trailers, which slammed into the back of the limo bus.
"The driver of the tractor-trailer failed to observe slow-moving traffic ahead," said Sgt. Gregory Williams of New Jersey State Police. "At the last minute, he swerved to try and avoid the Mercedes limo bus but struck it from behind, forcing the limo to rotate and overturn."
Kevin Roper, 35, the driver of the Walmart truck that caused the accident, was charged with one count of death by auto and four counts of assault by auto. He was being held on $50,000 bail.
Walmart President and CEO Bill Simon issued a statement about the accident.
"This is a tragedy and we are profoundly sorry that one of our trucks was involved," he said. "The facts are continuing to unfold. If it's determined that our truck caused the accident, Walmart will take full responsibility."