"To have someone dig a tunnel from below the shop into a display case is a very unusual case," Cologne spokesperson Chritoph Gilles told The Local.
As the 54-year-old owner of the Goldfinger shop in the northern suburb of Chorweiler entered his store on Monday, he noticed a hole in the floor of his display case. Police said that the hole was big enough for a person to fit in.
Gone were enough diamonds to leave the merchant with an estimated six-figure loss. The perpetrators left behind the display cases.
According to Gilles, the path of the crime showed that the thief or thieves first broke into a garbage room of a neighbouring building. From there, they were able to get into the basement through a trapdoor.
The thieves then bored through the cement and steel floor directly into a jewellery display case holding the gems.
Gilles said the owner didn't realize anything had happened until it was too late.
"There are security blinds on the shop's windows, so no one would have noticed anything until the shop opened up again," he said. That leaves the time frame for when the crime occurred anywhere between Saturday at 4.00pm when Goldfinger closed shop and when he opened up again on Monday morning.
Police are now appealing to witnesses who may have noticed anything between the various sites the perpetrator or perpetrators went through to pull off the heist.