The truck driver, 35-year-old Kevin Roper, of Jonesboro, Georgia, apparently failed to slow for traffic ahead and swerved at the last minute to avoid a crash, the Middlesex County Prosecutor's office said.
Instead, the big rig smashed into the back of the Mercedes limo bus, prompting a chain-reaction crash with a second tractor-trailer, an SUV and two cars, authorities said. No one in the other vehicles was injured.
So far, there is nothing to suggest Roper fell asleep or was dozing, state police Sgt. 1st Class Greg Williams told The Associated Press.
Roper, accompanied by his attorney, turned himself in to state police. He was released on $50,000 bail Saturday night, Wal-Mart spokesman David Tovar said Sunday.
Wal-Mart President Bill Simon said in a statement that the company "will take full responsibility" if authorities determine its truck caused the accident.
The National Transportation Safety Board said it was working with state police to look at any issues in the crash related to commercial trucking and limousine safety.
Tyrone Gale, who was driving the limo bus, told ABC News that he was disoriented after the vehicle flipped and could hear Morgan yelling for help.
"I climbed around and heard Tracy screaming for help," Gale said. "I climbed up on the body of the limo bus ... but I couldn't reach them."
Morgan's limo was owned by Atlantic Transportation Services, which said it had one employee behind the wheel and a second in the front passenger seat. Neither was injured.
"Although the investigation is still pending, we concur with the preliminary reports that the accident was caused by another vehicle traveling behind the Atlantic limo bus," the Rehoboth Beach, Delaware-based company said.
Fuqua had tweeted that he was opening for Morgan on Friday night at Dover Downs Hotel & Casino in Delaware. On his Instagram page, Fuqua included a collage of photos from the show.
"This is what it looks like from the stage to see a standing ovation from 1500 people," Fuqua wrote at around midnight Friday. "Then we traveled back to NYC in style in a luxury Mercedes Sprinter. Road life is a good life!"
Fuqua's mother, Doris, said she visited him in the hospital Saturday. The writer-comedian had toured with Morgan for nearly a year, she said.
"We're hoping for the best," Doris Fuqua said, adding that she didn't know how long he may be hospitalized. "It's too early to tell."
McNair, 62, of Peekskill, New York, was a close friend and mentor to Morgan, Morgan's ex-wife, Sabina Morgan, told the New York Daily News. "He was one of the first comedians that took Tracy under his wing," she said. "They were very close."