(CNN) -- A Georgia truck driver has been charged in a New Jersey wreck that left comedian Tracy Morgan in critical condition and another man dead, authorities said Saturday.
Kevin Roper, 35, of Jonesboro, was charged with one count of death by auto and four counts of assault by auto after the tractor-trailer he was driving crashed into the limo bus carrying the comedian and others, the Middlesex County Prosecutor's Office said.
Initial reports indicated there were seven people injured in the crash, but the prosecutor's statement put the number at four.
Morgan's condition was not expected to change Saturday, publicist Lewis Kay said. "His family is now with him and he is receiving excellent care."
Morgan, 45, was a regular on "Saturday Night Live" for seven years and received an Emmy nomination for his role on "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.
The wreck occurred at about 1 a.m. ET on Saturday on the turnpike in Mercer County, said Sgt. Gregory Williams of New Jersey State Police.
"NJSP says 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."
A limo passenger, 63-year-old James McNair of Peekskill, New York, was killed and three people besides Morgan were taken to the hospital, authorities said.
McNair was a comedian who performed under the name Jimmy Mack, said his sister, Valerie Daniel. "He spoke very highly of Tracy," she told CNN. "They go way back."
The prosecutor's statement said Morgan and two others, whose identities have not been formally released, remain hospitalized in critical condition. The remaining passenger was treated at the hospital and was released, the statement said.
Four other vehicles were involved in the crash, the prosecutors said, but the people in those vehicles were not injured.
Williams said he does not believe alcohol played a role in the accident, but that is under investigation.
Brooke Buchanan, a Walmart spokesperson, said the truck driver is a Walmart employee.
"This is a tragedy and we are profoundly sorry that one of our trucks was involved," said Bill Simon, president and CEO of Walmart U.S., in a statement. "The facts are continuing to unfold. If it's determined that our truck caused the accident, Walmart will take full responsibility."
The National Transportation Safety Board will investigate "safety issues related to commercial trucking and limousine safety," said agency spokesman Keith Holloway.
Christopher Thompson, spokesman for limo owner Atlantic Transportation Services, said driver Tyrone Gale, who is part owner of the company, was shaken up.
"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 and we are grateful that our drivers did not sustain life-threatening injuries," Thompson said.
Morgan performed a comedy tour act Friday night at the Dover Downs Hotel & Casino in Dover, Delaware, the venue said.
Thompson said he thought the limo bus was heading to drop Morgan off in New Jersey.
The actor received messages of support and concern on Twitter.
"Wishing a speedy recovery to our friend @RealTracyMorgan," tweeted SNL Weekend Update.
"Shocked to wake up and read that @RealTracyMorgan is injured. Love to Tracy and wishing him strength," said former SNL cast member Rachel Dratch.
"My thoughts are with Tracy Morgan and his family. I hope he pulls through this soon and gets back to making us laugh!" said Joan Rivers.
"Saying a prayer for @RealTracyMorgan," said actor-director Jon Favreau.
"Come on @RealTracyMorgan pull through this buddy," tweeted actor Ike Barinholtz of "The Mindy Project."
CNN's Rachel Wells, Suzanne Presto, Carma Hassan and Alexandra Field contributed to this report. CNN first learned of the accident from multiple Twitter users.