A witness told Agence France-Presse the gunman became irate "as his sandwich wasn't prepared quickly enough," shot the waiter, and then fled the scene.
The waiter's colleagues then called police after he was shot in the shoulder. The 28-year-old later died at the scene.
Area residents told Le Parisien newspaper the restaurant had opened three or four months before the deadly shooting. Some noted, however, the neighborhood has a high crime history, including drug-dealing and public drunkenness.
Others were shocked at the possibility of someone being killed over a slow order.
"It is sad," a 29-year-old woman told AFP. "It's a quiet restaurant, without any problems."