Andreas Lubitz, 28, from Montabaur in the west of the country, put the plane into a descent after locking the captain out of the cockpit, Marseille prosecutor Brice Robin told reporters.
He had reportedly joined Germanwings in 2013 and had logged only 630 hours flying time.
Asked about Lubitz's ethnicity, Robin said: "He was a German national and I don't know his ethnic background.
"He is not listed as a terrorist, if that is what you are insinuating."
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Pressed again on the co-pilot's religion, he said: "I don't think this is where this lies. I don't think we will get any answers there."
He said German authorities were taking charge of the investigation of Lubitz.
Robin said black box recordings showed that Lubitz "was breathing normally, it wasn't the breathing of someone who was struggling".
Speaking about whether the passengers realised what was happening, Mr Robin said: "I think the victims only realised at the last moment because on the recording we only hear the screams on the last moments of the recording."
He added: "I believe that we owe the families the transparency of what the investigation is pointing to and what is going on, we owe it to them to tell them what happened.
"The families have been informed of everything I just told you."
The recovered cockpit voice recorder gave information from the first 30 minutes of the flight.
For the first 20 minutes the two pilots talked in a normal fashion and were as courteous as two pilots would be.
He said the co-pilot's responses, initially courteous, became "curt" when the captain began the mid-flight briefing on the planned landing.
The captain is then heard asking the co-pilot to take over and the sound of a chair being pushed back and a door being closed is heard.
Moments later the captain can be heard knocking on the door and asking to be let in but there is no answer from the co-pilot.
Lubitz was a member of a flying club called LSC Westerwald.
The club posted a tribute on its website, that said: "As a youth, Andreas became a member of the society. He wanted to realise his dream of flying.
"He was able to fulfill his dream, the dream that cost him his life."
The statement continued: "We mourn Andreas and the other 149 victims of the catastrophe. Our thoughts are with the families.
"We will not forget Andreas."
Speaking at a press conference in Cologne, Lufthansa CEO Carsten Spohr said that Lubitz had broken off his training six years ago for several months, but that this was not unusual. He added that all pilots were subject to psychological vetting.
"No matter your safety regulations, no matter how high you set the bar, and we have incredibly high standards, there is no way to rule out such an event," Spohr told Reuters.