THE co-pilot of the German jet that went down in the Alps crashed the aircraft on purpose, killing all 150 people on-board.
Prosecutor Brice Robin named the co-pilot as Andreas Lubitz, a 28-year-old German.
He says he had no terrorist profile and when asked his religion he says "I don't think we should concentrate on [that] at this time."
The prosecutor says the information was pulled from the black box cockpit voice recorder, but the co-pilot did not say a word once the captain left the cockpit. "It was absolute silence in the cockpit," he said.
Prosecutor says he believes the co-pilot "voluntarily refused to open the door".
"No, this is not an accident," he said.
According to the Marseille prosecutor, whose briefing contradicts reports from a French aviation official in Le Monde earlier, the pilot banged on the door as the co-pilot accelerated the descent of the plane "intentionally".
"The intention was to destroy this plane," he said.
Germanwings Flight 9525 plunged from a cruising height of 38,000 feet to crash eight minutes later.
There had been 32 minutes of conversation on the black box found which had been analysed.
For the first 20 minutes the two pilots chatted amicably including about the eventual landing procedure.
After the pilot left to the go to toilet, the co-pilot activated the descent button.
The captain was then heard knocking and ringing the cockpit to get back in but his colleague was not answering, according to reports.
The copilot was alive though because his breathing could be heard.
Contact could also be heard from a ground air control tower but there was no response from the cockpit.
The New York Times was the first to report one of the pilots was not in command when the aircraft went down,
with the black box flight retrieved from the wreckage not making clear why he left and could not regain entry as the Airbus A320 aircraft steadily descended.
"The guy outside is knocking lightly on the door and there is no answer," an unnamed investigator told the Times, citing the recordings.
"And then he hits the door stronger and no answer. There is never an answer."
"You can hear he is trying to smash the door down," the investigator added.
According to the Independent, acquaintances said the pilot was in his late twenties and showed no signs of depression when they saw him last autumn as he renewed his glider pilot's license.
"He was happy he had the job with Germanwings and he was doing well," said a member of his glider club, Peter Ruecker, who watched him learn to fly.
"He gave off a good feeling."
Lubitz had obtained his glider pilot's license as a teenager, and was accepted as a Lufthansa pilot trainee after finishing a tough German college preparatory school, Ruecker said.
He described Lubitz as a "rather quiet" but friendly young man.
Plane hit the mountain at 700km/h
"Death was instant," says prosecutor Robin.
"It hit the mountain at 700km an hour. We only hear screams at the very end."
Mr Robin says the details about the co-pilot have only been known in the past "few hours" - adding that he is hoping for more information from the German side of the investigation shortly.
Prosecutor Robin confirmed that he has opened a formal investigation into 'voluntary homicide'.
Pounding could be heard on the door during the final minutes as alarms sounded.