The co-pilot of Germanwings Flight 9525 deliberately crashed the aircraft into the French Alps on Tuesday, according to officials at a press conference Thursday morning.

Marseille prosecutor Brice Robin reported the co-pilot, 28-year-old German national Andreas Lubitz, “wanted to destroy the aircraft” when he prevented the captain from re-entering the cabin after a bathroom break and “activated the descent” that resulted in the crash that killed all 150 passengers on board the flight traveling from Barcelona, Spain, to Düsseldorf, Germany, Tuesday.

Germanwings said the plane reached a cruising altitude of 38,000 feet and then dropped for approximately eight minutes before crashing after losing contact with French radar at a height of about 6,000 feet.

“We at Lufthansa are speechless that this aircraft has been deliberately crashed by the co-pilot,” said Carsten Spohr, CEO, Lufthansa, parent company of Germanwings.

Investigators are looking into why the co-pilot would crash the plane. According to Spohr, Lufthansa does “not have any clues.”

Data from the recovered cockpit voice recorder reveals the pilot and co-pilot had normal exchanges during the flight until the pilot left the cockpit for the bathroom and asked Lubitz to take over. According to Robin, Lubitz then “through deliberate abstention, refused to open the cabin door” and sent the plane into a dive.

The incident is not being described as a “terrorist attack” or a “suicide” either, according to officials. “If a person kills himself and also 149 other people, another word should be used — not suicide,” said Spohr.

Lubitz was not listed on any terrorism list, according to Robin.

With Germanwings since September 2013, Lubitz completed 630 hours of flight time and trained at the Lufthansa flight center in Bremen, Germany, according to the company. He had approximately 10 hours of experience on the type of aircraft he operated the day of the disaster and had all the necessary certifications and qualifications to pilot the plane alone, according to Robin.

Spohr revealed the pilot passed medical tests, but Lufthansa does not have standard psychological testing. The audio data reveals his breathing was steady at the time of the crash, with no signs of a medical issue.

Investigators are still studying voice recordings from one of the black boxes while the search continues for the second black box in the ravine where the plane crashed, located approximately 65 miles from Nice.

Check out next week’s eFlyer USA for a report on mental health testing for airline pilots.