BERLIN (AP) — The father of Germanwings co-pilot Andreas Lubitz said Friday his son loved life and wasn't suffering from depression on the day his plane crashed in the French Alps, killing all 150 people on board, suggesting the official investigation's conclusions were faulty.

Guenter Lubitz said he was speaking publicly for the first time to challenge claims by French and German authorities, who have concluded that his son slammed the Airbus A320 into a mountainside in order to kill himself.

"In the six years before the crash we knew our son as someone who loved life," Guenter Lubitz told reporters in Berlin. "Our son wasn't depressed at the time of the crash."

Other families who lost loved ones in the crash on March 24, 2015, have expressed anger at the news conference, on the second anniversary of the crash. German prosecutors dismissed the suggestion that their investigation of the crash — which focused on possible negligence by third parties — had failed to examine all reasonable leads.

Duesseldorf prosecutor Christoph Kumpa told The Associated Press that Lubitz had suffered from depression during his pilot's training, but that there was no indication this had persisted beyond 2009.

"However, the investigation showed that from the period after the end of December 2014 symptoms were found that indicated that a new psychological illness had arisen at the time, which was diagnosed by specialist doctors in February and March 2015," Kumpa said.

He said that while Lubitz wasn't diagnosed with depression, he had been suffering from "another psychological illness that is commonly also treated with anti-depressants." Evidence that the co-pilot was taking such medication was found after the crash, he said.

A review of Lubitz' tablet computer showed he had also searched for information on the cockpit door in the week before the crash. Investigators concluded that the co-pilot had locked the captain out of the cockpit before setting the plane to fly at the lowest possible altitude.

"In the view of Duesseldorf prosecutors there can be no reasonable doubt that the co-pilot intentionally and voluntarily caused the crash for suspected suicidal reasons," said Kumpa.

An aviation expert commissioned by Guenter Lubitz told reporters that authorities had failed to pursue several other possibilities in their investigation, including technical errors and hazardous weather conditions.

The expert, Tim van Beveren, accused authorities of "poisoning" the investigation by concluding two days after the crash that Lubitz was responsible. He urged authorities to review the case again and give the co-pilot's family access to documents previously unavailable to them.

A spokesman for the German transport ministry said Friday that the government saw no reason to doubt the results of the investigation that had concluded Lubitz crashed the plane intentionally into a mountainside.

Guenter Lubitz insisted that he hadn't chosen to hold the news conference on the anniversary of the crash "to hurt the other families," some of whom were gathered near the site of the crash for a memorial ceremony Friday.

"Like all other families we too are looking for truth," he said.