Authorities say the man walked into the restaurant with a gun, looking for cash.
The restaurant had just opened for business, when police say the suspect flashed his gun to employees only and asked to see the manager.
He then ran out the front door with the money.
"Provided what I would call a ruse to get access to the restaurants safe room," Cary Police Lt. John Szymeczek said.
Teresa Shaw and her family were inside the Red Lobster minutes after the robbery happened.
"If we had probably been early, that would have been there when it happened, glad we waited a bit," Shaw said.
At first, she says everything seemed fine, until police showed up in the parking lot.
"After that they didn't let anybody in and then of course we were told we would have to wait and be walked out, "Shaw said.
Cary police are still searching for the suspect, but only have a vague description.
Investigators are also trying to figure out if he used to work there or how he knew about the safe room.
"Certainly a possibility, a reasonable question to ask I'm not familiar with safe rooms in restaurants per say, so that is something were looking into," Lt. Szymeczek said.
The Red Lobster re-opened for business around 1 p.m. Sunday.