Just for clarification, I'm a french writer and journalist, living in Brussels.
As far as we know (Thu. morning, 1136, Paris time), it was the FO who was blocked outside, and the captain inside flight deck.Both were speaking in german prior to the incident. When banging on the door, the FO receives no reply, no reaction apparently.
Source : Le Monde.fr
Crash de la Germanwings : le copilote était coincé à l'extérieur du cockpit avant l'accident