The co-pilot who authorities say deliberately crashed Germanwings Flight 9525 into the French Alps, killing all 150 aboard, had battled depression and burnout in the past, his friends told the German magazine Der Spiegel.

Andreas Lubitz, the 28-year-old co-pilot who investigators believe locked the Germanwings pilot out of the cockpit and intentionally flew the Airbus A320 into a mountain, took a break in 2009 from his lifelong pursuit of flying because of the condition, according to the magazine. But he soon resumed the ambition that had gripped him from an early age.

“He was happy he had the job with Germanwings and he was doing well,” said a member of Luftsportclub, Peter Ruecker, who watched Lubitz learn to fly. “He gave off a good feeling.”

Police on Thursday were swarming the home of Lubitz's parents in Montabaur, a town about 60 miles northwest of Frankfurt. Residents who knew Lubitz were dumbfounded that their neighbor would commit such a monstrous act.

Lubitz's "big dream was from the beginning to become a pilot," one woman told the Rhein-Zeitung. "He pursued this goal with vigor and reached it.”

Another neighbor told the BILD, “I refuse to believe it before it is 100 percent proved.”

Officials say Lubitz has no known ties to terror, and Germanwings' parent company Lufthansa said Thursday he had shown no outward psychological problems that could explain why he would intentionally take down a plane full of people. French prosecutor Brice Robin said the cockpit voice recorder shows Lubitz breathing normally in the final moments before the plane crashed.

“His breath was not of somebody who was struggling,” Robin said. “He never said a single word. It was total silence in the cockpit…. Nothing.”

Robin said Lubitz refused to open the cabin door to veteran pilot Patrick Sonderheimer, who had left apparently to use the bathroom. The plane crashed in a remote region of the French Alps, killing all 150 on board, after an 8-minute descent with Lubitz acting calmly in the cockpit, Robin said.

Lubitz began flying with Germanwings in 2013 and had 630 flight hours.   After completing his training, Lubitz spent an 11-month waiting period working as a flight attendant before becoming a co-pilot on the Germanwings A320 fleet. Spohr said such a waiting period is not unusual at Lufthansa.

Lufthansa CEO Carsten Spohr told reporters in Cologne Thursday Lubitz’s training included rigorous psychological testing. He said pilots undergo yearly medical exams, but those don’t include psychological tests.

Spohr said Lubitz “was 100 percent fit” to fly. ”There was no particular thing to note or to watch out for,” he said.

The CEO confirmed that, after Lubitz qualified as a pilot in 2008, he took a break from training six years ago. Spohr said he did know why.

“We choose our staff very strictly,” the executive said. 

In January, 2012, the FAA issued Lubitz a license to fly single-engine private planes and gliders.

Lubitz began flying gliders when he was 14. He renewed the license last year. Friends said he had a girlfriend and was an avid runner.

The Wall Street Journal said Lubitz finished in the top 75 out of 780 participants in a 10-kilometer post-New Year’s run in Montabaur in 2007. He raced alongside his then 54-year-old father, Günter Lubitz.

He and his father also ran the Lufthansa Frankfurt half-marathon in 2011, 2012 and 2013.