A barricade device and a method of barricading a door are disclosed. The device and method may be used to barricade a door, and thereby prevent an intruder from entering a sheltering space, such as a classroom, storeroom, or hallway. The barricade-device may have a pivotable stop-device that is pivotable from a location adjacent to a door. The pivot-location may be at an elevation that is lower than a door handle on the door. The stop-device may be pivotable from a reserve-position to a stop-position. In the reserve-position, the stop-device does not barricade the door. In the barricade-position, the stop-device barricades the door.