tracymorgan04_JPG.jpg

Actor and comedian Tracy Morgan was critically injured in a crash on the Turnpike on Saturday.

(Star-Ledger file)

By Tom Wright-Piersanti/The Star-Ledger

and Brian Amaral/NJ.com

The top executive at Walmart admitted that one of his company's trucks was involved in a six-vehicle crash Saturday that killed one man and critically injured three others, including comedian and actor Tracy Morgan.

“The facts are continuing to unfold," CEO Bill Simon said Saturday. "If it’s determined that our truck caused the accident, Walmart will take full responsibility."

James McNair, a 62-year-old comedian from Peekskill known as Jimmy Mack, was killed in the crash, authorities said Saturday. McNair also wrote for Morgan and was one of his closest friends.

According to a Robert Wood Johnson University Hospital spokesman, Morgan, 45, assistant Jeffrey Millea, 36, of Shelton, Connecticut, and comic Ardie Fuqua, 43, of Jersey City, remain in critical condition this morning.

Another comedian, Harris Stanton, 37, of Brooklyn, was treated and released from the hospital.

Truck driver Kevin Roper, 35, has been charged with one count of death by auto and four counts of assault by auto in the accident, the Middlesex County Prosecutor's Office said.

Roper, accompanied by his attorney, turned himself in to State Police on Saturday night, according to the Associated Press. He was processed and turned over to Middlesex County officials. Roper lives in Jonesboro, Ga.

A court appearance is expected Monday, but has not yet been scheduled, a spokesman for the prosecutor's office said.

Simon said he was "profoundly sorry" that a Walmart truck was involved in the accident, and the company said it is cooperating fully with law enforcement.

Morgan, Fuqua, Millea and Stanton were traveling from a gig at Dover Downs Casino in Delaware early Saturday when their 2012 Mercedes-Benz Sprinter van was struck by Roper's truck on the New Jersey Turnpike, according to State Police.

Morgan's driver Tyrone Gale told ABC News that the impact felt like an explosion, after which the van felt like it flipped several times.

"I climbed around and heard Tracy screaming for help," Gale told ABC. "I climbed up on the body of the limo bus ... but I couldn't reach them."

"I can only say feeling helpless on the highway was very hard to take. There was nothing I could do but scream at times," Gale said in a post to his Facebook page. "This is not something I will be able to forget in my lifetime."

Four other vehicles were involved in the crash, but none of their occupants was seriously injured. The National Transportation Safety Board is investigating the crash.

Morgan first gained prominence as a “Saturday Night Live” cast member. He went on to star in the critically acclaimed television series “30 Rock."

Morgan's ex-wife, Sabina Morgan, told the New York Daily News that McNair was an important part of Morgan's career. "He was one of the first comedians that took Tracy under his wing," she said. "They were very close."

Royale Watkins, a Los Angeles-based comedian who said he had performed in New York clubs with Morgan and McNair, described McNair as having a big personality.

"There may be guys like Tracy who get the fame and notoriety, but you have people like Jimmy Mack who have kind of energized and fueled cats like Tracy and kept them going on the road," Watkins said.

The prosecutor’s office asks that anyone with information about the crash to call the State Police’s Detective Bureau in Cranbury at (732) 609-860-9000, ext. 4400.

The Associated Press contributed to this report.