Two men, dressed in Santa hats and masks, surprised and attacked the guard.

The men stole the guard’s gun, which according to police was a loaded automatic weapon.

“This is serious. I have a hard time believing it is a prank. It might be premeditated,” said Anders Krook, station commander at the Norrmalm police.

Because the Royal Palace has been deemed an object to be protected (skyddsobjekt), guards are to have loaded weapons, Lieutenant Colonel Rickard Beck-Friis Häll told TT news agency.

After the incident on Thursday, they will review all of the regulations with the soldiers, including the level of force that the guards may use.

“We have the right to use the force that is necessary to defend ourselves and objects to be protected. In this case, we will review what happened,” Beck-Friis Häll said.

He emphasized that the event was extremely unusual and he has never hear of a similar incident during his 30-year-career.

At night, two guards are posted the Royal Palace , and they are both armed with an AK-5 with a bayonette. They are posted so that they are within sight of each other, according to Beck-Friis Häll.

Since he doesn’t know the details, he refrained from commenting on last night’s event, but said there are procedures in place the guards are to follow in such situations.

“I don’t know what level of force the robbers used and if they threatened, but firing a gun in the last course of action,” Beck-Friis Häll said.