The New York Times - "An Epidemic Of Carjackings Afflicts Newark" - Dec. 29th, 2013:

Out front, a couple of regular customers pulled up in a Mercedes-Benz E350. The passenger got out, but the driver remained behind the wheel, talking on a cellphone. Nearby, four young men lingered, their faces covered with scarves and hoods, eyeing the car as they walked past it twice, the store owner recalled.

One of the men jumped into the passenger seat and told the driver to get out, the store owner said. The driver resisted...A shot was fired. The men fled, leaving the car behind and its driver wounded.

Though it's not stated explicitly, it seems clear that the carjacker "jumped into the passenger seat" after opening the unlocked door on the passenger's side of the car.