Police say the two victims were carjacked and robbed inside the garage. The female victim was then forced to drive to an alley near Martin Luther King Boulevard.
According to investigators, Rattu was shot and killed in the alley, while Ghetia was expected to survive.
Police say three people fled the scene. Authorities released photos of men they are calling persons of interest in the case.
Investigators now say they are looking for a gray Saturn Ion with New Jersey license plates UTN 66U.
The car was stolen from Haddonfield last month.
Family said Rattu and Ghetia were celebrating in Atlantic City after Rattu had just graduated nursing school.
"This is a senseless killing, there was no reason," said one family member.
Authorities are asking anyone with information about the incident to contact the Atlantic County Prosecutor's Office Major Crimes Unit at 609-909-7899 or the Atlantic City Police Department Detective Bureau at 609-347-5766.