Debris from the plane crash. Photo by F. Balsamo – Gendarmerie nationale / Ministere de l’Interieur via Getty Images.

The co-pilot of the Germanwings flight that crashed into the French Alps Tuesday intentionally put the aircraft into a dive, the Marseille prosecutor handling the investigation said Thursday.

The co-pilot was breathing until the moment of impact, but did not utter a word during the 10-minute final descent, said the prosecutor, Brice Robin, at a press conference. “The intention was to destroy this plane,” he said.

The co-pilot—named as Andreas Lubitz, 28, of Germany—was alone in the cockpit because the pilot had “left to make a ‘natural call.'” The pilot can be heard on the cockpit voice recorder banging on the door in an attempt to get back in.

Just before impact, cries from passengers can also be heard on the recorder, Robin said. “The death would have been sudden, immediate.”

Robin said there was no indication that it was a terrorist attack, but stopped short of calling it a suicide. “I can’t call this a suicide, but it is a legitimate question to ask,” he said.

Lubitz first worked as a flight attendant and began training 2008. Carsten Spohr, the chief executive of Lufthansa, Germanwings’ parent company, said Lubitz’s training results weren’t unusual, the Guardian reported.

An investigation into Lubitz’s background is ongoing, The New York Times reported.

A mother and daughter from Nokesville, Va.—Yvonne and Emily Selke—were among the 150 passengers who died in the crash. In a statement Tuesday, the family asked for “privacy and your prayers.”

The flight was headed from Barcelona to Dusseldorf.