Delft community policing forum chairperson Reggie Maart reportedly said there had been a recent "scourge" of shootings in the area.
The Cape Argus reported that Jarryd Manuel and his girlfriend Megan Hendricks (19) were shot outside his mother's home in Delft on Sunday evening.
Captain Frederick van Wyk told the newspaper a 19-year-old man had been taken in for questioning in connection with the shooting.
Manuel was a PAY Project intern in the Centre for e-Innovation at the premier's department.
"This is a tragic and senseless death that highlights just how serious the crisis of gang violence is," Zille told the Cape Argus.
"Jarryd … could have undoubtedly built a successful career for himself using the opportunity offered by his internship."
Zille sent condolences to the couple's family and friends.
Delft community policing forum chairperson Reggie Maart reportedly said there had been a recent "scourge" of shootings in the area, with at least five dead and another two wounded since last Monday.
"This area of Delft is wedged right between strongholds of a number of gangs. The shootings are often related to battles for drug dealing and control of turf," he was quoted as saying.
He said innocent people were often caught in the crossfire. – Sapa