In a new documentary, the tragic crash of Germanwings Flight 9525 is revisited, providing a closer look at the terrifying moments just before co-pilot Andreas Lubitz purposefully crashed the aircraft into the French Alps.

What started out as a normal trip from Barcelona to Düsseldorf on March 24, 2015, descended into an unthinkable tragedy. All 150 passengers and crew members were killed when the Airbus A320 crashed at 430 mph less than an hour after takeoff.

The crash’s intentionality was later confirmed by investigators. Prior to starting the deadly descent, Lubitz, who had a history of depression and suicidal thoughts, waited until he was by himself in the cockpit.

The Calculated Act
Shortly after 10 a.m. local time, flight 9525 took off. After about half an hour, Lubitz was left alone at the controls when Captain Patrick Sondenheimer left the cockpit to use the restroom. According to the BBC, Lubitz locked the door as it clicked shut behind him, reduced the altitude from 38,000 feet to just 100 feet, and started the plane’s last descent.

Later, black box recordings showed that Lubitz disregarded air traffic control’s repeated attempts to establish contact. Sondenheimer, meanwhile, is heard frantically pounding on the cockpit door while yelling, “Open the damn door!” in an attempt to regain control.

To make sure nobody else could get in, Lubitz had overridden the emergency access codes.

Last Words
The recorder captures the screams of passengers in the final moments of the flight, just before the aircraft crashes into the mountainside.

Additionally, the black box captured Lubitz’s earlier statements, such as a seemingly ordinary conversation in which he tells the captain, “You can go now,” after being given command of the aircraft.

It was discovered after the crash that Lubitz had lied to his employer about being deemed unfit to fly by a physician. Lubitz once stated (via CBS News): “One day I will do something that will change the whole system, and then everyone will know my name and remember it,” according to a former girlfriend who later told a German newspaper.

The official investigation’s conclusions were rejected by Lubitz’s family, who maintained that he had passed out prior to the collision. Nonetheless, the conclusion that the crash was premeditated has been broadly supported by the evidence from the cockpit voice recorder.

#Germanwings pilot Andreas Lubitz practiced descent on previous flight, investigators confirm http://t.co/EwjEdGN25X pic.twitter.com/SA6LVu83E0

— BBC Breaking News (@BBCBreaking) May 6, 2015

The incident led to an overhaul of aviation safety protocols, including stricter rules requiring two people to be present in the cockpit at all times.