And it all went down incredibly simply:
At approximately 11:30am, investigators say that the lone robber entered through a French doorway at the side of the Carlton Intercontinental Hotel in Cannes.
The door was not broken into, so police are uncertain if the thief somehow jimmied it open or if it had been accidentally left open by staff or guests.
He then made his way into a temporary jewelry exhibit that was being held over the summer in the hotel. It housed jewels and diamonds from the Leviev diamond house owned by Israeli billionaire Lev Leviev. The exhibition had been highly publicized in the area, according to 5 Eyewitness News.
There were only three private security guards, two vendors, and one manager on site, whom the thief threatened with the handgun (it remains unclear if the private security guards were armed at the time).
The thief then grabbed a bag containing a briefcase and small box that was filled with valuable jewels like earrings and pendants, according to Philippe Vique, the assistant prosecutor in the nearby town of Grasse.
With his loot in tow, the robber ran through a side door and jumped three feet onto a terrace next to the hotel, before dodging down a nearby side street.
The whole heist was over in a minute. The brazen thief got away with approximately 72 pieces of jewelry including rings, earrings, and pendants (though he dropped a few in his hasty exit).
Security cameras caught the man on camera, but he had covered his face with a scarf and cap, and wore gloves.
And that's how easily $136 million worth of diamonds and jewels was stolen on the French Riviera.