It happened Saturday in Parking Lot B as traffic left the venue.
Detectives said a red Dodge Ram pickup with black rims and black grill and a silver F-150 with amber lights in a black grill may have information that could advance the investigation.
"Somebody was just knocked out in the middle of the parking lot," a 911 caller told dispatchers.
She said some people jumped out of a truck and "knocked the guy out."
The caller told the dispatcher that people continued fighting after the man was hit.
Anyone who may have witnessed the assault or who has information that might assist the investigation of the incident is asked to call Raleigh CrimeStoppers at (919) 834-HELP or visit raleighcrimestoppers.org for text and email reporting options. CrimeStoppers pays cash rewards for anonymous tips that help solve cases.