A person familiar with the investigation told the Journal that Lubitz was not only being treated for depression, but also hid news of his treatment from his employer - Lufthansa's low cost subsidiary Germanwings.
Investigators believe Lubitz locked the flight's captain out of the cockpit as the 28-year old junior co-pilot flew the Airbus A320 airliner into a mountainside.
According to the Wall Street Journal source, there is no evidence that would indicate Mr. Lubitz was on any "mind-altering medication" at the time of the incident.
Breaking: Germanwings co-pilot was being treated for depression and tried to conceal that from employer Lufthansa http://t.co/tYCeELTJqc
- Wall Street Journal (@WSJ) March 27, 2015
Lubitz reportedly ripped up medical leave notes that had been issued to him and according to Germanwings were not submitted to the airline.