Witnesses said the killer produced a handgun and shot the 28-year-old waiter at Le Mistral restaurant in Noisy-le-Grand, east of Paris, because his “sandwich wasn’t prepared quickly enough”.
The employee was seriously wounded in the shoulder.
Paramedics who arrived at the scene were unable to revive him and was pronounced dead.
Police have opened an investigation into the case.
Shocked residents gathered outside the pizza and sandwich eatery on Saturday. “He was killed for a sandwich?” one asked, unbelievingly.
“It is sad,” said a 29-year-old woman. “It’s a quiet restaurant, without any problems. It just opened a few months ago.”
But others noted high crime levels in the area, notably drug-dealing and public drunkenness.