UPDATE, 9:08a ET: A French prosecutor explained in a press conference this morning that the co-pilot of the Germanwings flight appears to have deliberately crashed the Airbus.

Brice Robin, a Marseille prosecutor, said that the plane's co-pilot, 28-year-old Andreas Lubitz, didn't seem distressed in the flight's final 10 minutes before it crashed on Tuesday in the French Alps.

Read more about this latest development here

The New York Times reported that a pilot was locked out of the cockpit of the Germanwings A320 plane which crashed Tuesday.

Evidence from a cockpit voice recorder reportedly reveals that one of the pilots left the cockpit and was unable to return.

Read more from the New York Times:

A senior military official involved in the investigation described “very smooth, very cool” conversation between the pilots during the early part of the flight from Barcelona to Düsseldorf. Then the audio indicated that one of the pilots left the cockpit and could not re-enter.

“The guy outside is knocking lightly on the door and there is no answer,” the investigator said. “And then he hits the door stronger and no answer. There is never an answer.”

He said, “You can hear he is trying to smash the door down.”

While the audio seemed to give some insight into the circumstances leading up to the Germanwings crash, it also left many questions unanswered.

"We don’t know yet the reason why one of the guys went out,” said the official, who requested anonymity because the investigation is continuing. "But what is sure is that at the very end of the flight, the other pilot is alone and does not open the door."

GRN’s Catherine Field went “On The Record” to discuss this revelation, calling it “another piece of this very large jigsaw.”

The A320 plane crashed in the French Alps on its way from Spain to Germany. All 150 people aboard the plane were killed.

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