He then "calmly" left the Harry Winston store.
A robber took $16 million in diamonds from a jewelry store in Cannes, France, authorities said.
The man, armed with a handgun and a grenade, then "calmly escaped on foot," Reuters reported. It's not yet clear whether the grenade was genuine.
The Associated Press reports that the store was a Harry Winston location. The merchandise stolen included diamond necklaces along with other jewelry, according to AP.
The robber initially posed as a customer before showing the gun an instructing two salespersons to open the jewelry cases, Reuters reported. The culprit wore sunglasses but otherwise did not hide his face, a prosecutor said.
No injuries were reported in the robbery.
Cannes is located on the French Riviera. The store is located within the city's Croisette waterfront area.
Don't Gamble with Your Retirement
Let Wilkerson manage every detail of the most important sale of your life.