Story highlights The theft takes place as police are busy supervising New Year revelers

The armed robbers force their way in and seek out iPhones and iPads

"They knew exactly what they were taking," a police union official says

The masked intruders assaulted store employees during the robbery

The robbers, police say, were "well informed" and had carefully chosen the time and place of their heist.

As police officers were busy keeping an eye on areas popular with New Year revelers, four armed and masked robbers forced their way into an Apple store in central Paris and made off with as much as $1.3 million worth of iPhones, iPads and other devices.

The robbers entered through a service entrance into the store, which had closed for the day, using violence to intimidate store employees, said Agnes Thibault-Lecuivre, a spokeswoman for the Paris prosecutors office.

They then "calmly" went through boxes full of Apple products in the basement storeroom, seeking out iPhones, iPads and laptops, said Christophe Crepin, spokesman for UNSA Police, a national police trade union.

"They knew exactly what they were taking," he said, noting that the robbery focused on the merchandise in the storeroom and left the devices on display inside the store untouched.

They loaded the stolen goods, estimated to have a retail value of around one million euros ($1.3 million), into a Mercedes van parked nearby and sped off, he said.

Thibault-Lecuivre declined to confirm the value of the robbers' haul, saying that Apple managers were still working out how much had been taken.

Housed in an elegant Haussmann-style building in a popular shopping district, the store Apple Store at Opera is one of two in central Paris. The other is in an underground mall connected to the Louvre.