Officers said one of the victims was identified as Self’s daughter, Katelyn Self, 26, who worked with the Gaston County Sheriff’s Office.
Other family members were also injured, according to police.
"Tragic, tragic loss of life,” Gaston County Sheriff Alan Cloninger said. “I'm asking people just to keep the family in your prayers, and the Sheriff's Office, because we're suffering right now."
Caleb Martin, who is just 14 years old and buses tables at the restaurant, witnessed the car crash through the building.
"I walked over to my station and I heard a loud boom,” he said. “It went straight through. There's a doorway. There is a wall and he drove in another room."
Caleb was dazed by the carnage he saw.
He said that momentarily he didn't know what to do but then sprang into action.
"The one guy I could help in back, he was pretty hurt,” Martin said, “I helped paramedics move tables off this dude and I moved debris out of the way so they could get to him."
Officials said Roger Self is a private investigator who used to work for the Gastonia Police Department years ago.
Police said all of the victims, and Roger Self, are known to the employees.
"He was a regular and we haven't seen him in a while, so when he came back, it was kind of sad,” Martin said.
This is a developing story. Check back with WSOCTV.com for updates.