(JTA) — The theft of diamonds and jewels owned by Israeli billionaire Lev Leviev could be the largest jewelry heist in years after the worth of the stolen jewels was estimated at $136 million.

A masked gunman stole the diamonds and jewels from an exhibition at a luxury resort in Cannes on Sunday afternoon. The thief threatened the exhibition staff and visitors at the Carlton Hotel, filled a briefcase with the jewels and fled in an operation that lasted about a minute, police told the Associated Press. Immediately following the robbery, police estimated the value of the stolen jewels to be $53 million. A more complete inventory of the stolen jewelry puts the value at some $136 million, the AP reported Tuesday.

Private security guards had protected the exhibit.

The display about the Leviev diamond house at the prestigious Carlton Hotel had been scheduled to run through August.