Marignane - The co-pilot of the doomed Germanwings flight appears to have deliberately crashed the plane after locking his captain out of the cockpit, French officials said, with the "unimaginable" development sparking global shock and anger among victims' loved ones.
In a chilling account of the final minutes of Germanwings Flight 4U 9525, lead prosecutor Brice Robin said on Thursday that 28-year-old German Andreas Lubitz initiated the plane's descent into the French Alps while alone at the controls.
Lubitz appeared to "show a desire to want to destroy" the plane, Robin told reporters after his team analysed the Airbus A320's cockpit voice recorder.
The first officer, who was described by neighbours and fellow flying club members as a "friendly" guy-next-door type who enjoyed jogging with his girlfriend, was not however believed to be part of a terrorist plot, officials said.
German Chancellor Angela Merkel said the revelation added an "absolutely unimaginable dimension" to Tuesday's tragedy, in which 150 people were killed, mostly German and Spanish nationals.
It prompted airlines to review their cockpit policies, many announcing they will now require two crew members in the cockpit at all times.
Spain's Prime Minister Mariano Rajoy said he was "deeply shaken" by the news and sent his "heartfelt affection" to the victims' families, dozens of whom had arrived near the crash site.
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They were briefed by the prosecutor, who said they reacted with "shock" to the findings.
Robin said the passengers were killed "instantly" by the crash and were probably unaware of the impending disaster until the "very last moment."
"The screams are heard only in the last instants before the impact," he said.
"The co-pilot was alone at the controls," he said. "(He) deliberately refused to open the door of the cockpit to the pilot."
The pilot, believed to have gone to the toilet, made increasingly furious attempts to re-enter the cockpit, banging on the door, the recordings appear to show.
In the northwestern German town of Haltern, which lost 16 students and two teachers killed while returning from a school exchange, the revelations caused shock and anger.
"Personally, I'm stunned, angry, speechless and deeply shocked," Haltern's mayor Bodo Klimpel told a news conference.
"I'm asking myself when this nightmare will end. It's bad enough for the families to learn of the death of loved ones in an accident. But when it's clear that an individual may possibly have deliberately caused the accident, it takes on an even worse dimension," Klimpel said.
The shaken principal of the stricken school, Ulrich Wessel, said "what makes all of us so angry (is) that a suicide can lead to the deaths of 149 other people ... It leaves us angry, perplexed, stunned."
The head of Germanwings' parent company Lufthansa, Carsten Spohr, said that "in our worst nightmares we could not have imagined that this kind of tragedy could happen to us".
A man in this 50s who gave his name only as Hans-Dieter travelled to the western German town of Montabaur to see Lubitz's home where he lived with his parents.
"I wanted to know where the murderer lived," he said.
Controls set to 'accelerate' descent
The French prosecutor downplayed the likelihood of Lubitz accidentally taking the plane down with an involuntary turn of the descent button.
"If you passed out and leaned over on it, it would only go a quarter-way and do nothing," Robin said, adding Lubitz, who had worked for Lufthansa since 2013, had set the controls to "accelerate the plane's descent."
For the eight minutes after he began the descent, Lubitz was apparently calm and silent, breathing normally and showing no sign of panic.
"He does not say a single word. Total silence," Robin said.
The co-pilot's motive remains a mystery.
"At this moment, there is no indication that this is an act of terrorism," Robin said, an assessment echoed by Germany's Interior Minister Thomas de Maiziere.
Lufthansa's Spohr said there wasn't "the slightest indication what might have led" to the Lubitz's actions.
The second-in-command had passed all psychological tests required for training, Spohr told a press conference, insisting: "He was 100-percent airworthy".
The search for clues saw investigators on Thursday search Lubitz's home as well as the flat he kept for work in the Germanwings hub of Duesseldorf.
Changes to cockpit policy
In the first industry responses to the disaster, Canada ordered its airlines to have two people in cockpits at all times, effective immediately.
Germany's aviation association BDL announced plans Thursday to introduce a two-person cockpit rule, while British low-cost carrier easyJet, Scandinavia's Norwegian Air Shuttle and Icelandair all made similar announcements.
Also read: Germanwings co-pilot lived quiet life
Many US airlines already have such a policy in place.
The International Civil Aviation Organization, the United Nations world aviation body, called for regular mental and physical check-ups for pilots.
Meanwhile, families and friends of victims gathered near the remote mountainous crash site area in the French Alps.
Tents were set up for families to give DNA samples to start the process of identifying the remains of the victims, at least 50 of whom were Spaniards and at least 75 Germans.
Remains found scattered across the scree-covered slopes were being taken by helicopter to nearby Seyne-les-Alpes.
One investigator said the operation would take at least a fortnight.
The crash site, which is situated at about 1 500m altitude, is accessible only by helicopter or an arduous hike.
Lufthansa said the aircraft was carrying citizens of 18 countries. The dead also included two babies.
A second black box, which records flight data, has not yet been recovered.