A truck driver charged in a weekend crash that killed a man and injured comedian Tracy Morgan and others in New Jersey was awake for more than 24 consecutive hours before the incident, a criminal complaint filed in the case says.

Kevin Roper, 35, is charged with vehicular homicide and assault by auto in the Saturday morning crash on the New Jersey Turnpike.

The wreck took place about 1 a.m. Saturday when the limo van Morgan was in was hit by a tractor-trailer on the New Jersey Turnpike, police said.

The collision killed Morgan's fellow passenger, comedian James McNair -- who performed under the name Jimmy Mack.

Comedians Ardie Fuqua and Harris Stanton were among the injured, as was a man named Jeffrey Millea.

Morgan's publicist said he's showing signs of improvement.

"He has been more responsive, which is an incredibly encouraging sign," publicist Lewis Kay said Sunday.

Morgan's injuries

Morgan suffered several injuries, including broken ribs, a broken nose, a broken leg and a broken femur.

Kay, the publicist, said Morgan underwent surgery on his leg Sunday.

"We expect him to remain in the hospital for several weeks," he said.

The truck driver

The truck driver charged in the crash turned himself in to police, and was released on a $50,000 bail Saturday night.

Roper was a driver for Walmart.

"This is a tragedy, and we are profoundly sorry that one of our trucks was involved," Bill Simon, president and CEO of Walmart U.S., said in a statement.

"The facts are continuing to unfold. If it's determined that our truck caused the accident, Walmart will take full responsibility."

Chain-reaction crash

The wreck occurred about 1 a.m. ET Saturday on the turnpike in Mercer County, said Sgt. Gregory Williams of New Jersey State Police.

"The driver of the tractor-trailer failed to observe slow-moving traffic ahead," Williams said. "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."

Four other vehicles were involved in the crash, the prosecutor's office said, but no one in those vehicles was injured.

Williams said he does not believe alcohol played a role in the crash, but that is under investigation.

The National Transportation Safety Board will investigate "safety issues related to commercial trucking and limousine safety," said agency spokesman Keith Holloway.

"All I know is I saw traffic ... and I stopped ... and I was upside down and in the vehicle," limo driver Tyrone Gale told WCAU.

Gale suffered bruises in the crash, WCAU reported.

Christopher Thompson, the co-owner of Atlantic Transportation Services, which was operating the limo bus, said he thought the bus was heading to drop Morgan off in New Jersey.

From SNL to '30 Rock'

Morgan, 45, was a regular on "Saturday Night Live" for seven years. He later received an Emmy nomination for his role in the comedy series "30 Rock," in which he played Tracy Jordan, an exaggerated version of himself.

The New York City native made his reputation with over-the-top characters and impressions of celebrities such as Mike Tyson and Oprah Winfrey.

Morgan performed a comedy act Friday night at the Dover Downs Hotel & Casino in Dover, Delaware, the venue said.

Kay said Morgan's family "is tremendously overwhelmed and appreciative of the outpouring of love and support from his fans."