As investigators search for clues as to why Germanwings co-pilot Andreas Lubitz crashed a passenger plane into the French Alps on Tuesday, the key may lie in his past, one expert says.

On Friday, a German newspaper reported that Lubitz, 27, of Montabur, Germany, may have just broken up with his girlfriend. Prosecutors reported he was being treated for a medical illness he kept hidden from his employer, and German newspaper Bild published alleged details of his medical records, including that he had been diagnosed with a “severe depressive episode” in 2009 when he halted pursuit of a pilot’s license.

Officials haven’t confirmed whether Lubitz had been suffering from depression or had recently ended a relationship. But if both are true and the breakup expedited his spiral, there are individuals who are sensitive to abandonment or perceived abandonment, which may explain his actions, said Dr. Keith Ablow, psychiatrist and member of the Fox News Medical A-Team.

“Very often, these are people who have suffered abandonment at critical points in their lives earlier, sometimes during childhood,” Ablow told FoxNews.com. “The forensic psychologists who look at this case should be alert to whether this man had been sensitized by early losses to register abandonment very, very deeply.”

People who are depressed may be living on the edge of decisions about life and death, and one more negative event could be enough to make them believe there’s no hope in the world, Ablow said.

“Because depression is so thematically powerful and so dark, when it’s very severe, it can make people feel not only as if they’ve lost a loving connection, but as if the whole world is devoid of love,” Ablow said. “So if we wonder how somebody could take 149 people with him when he commits suicide, one answer can be that depression, when it’s most severe, can make people feel that life is completely without value, not just for them but for anyone.”

Severe cases of depression may cause people to feel they are responsible for all the evil in the world, or that other people are evil, or that it’s better that tomorrow not come for anyone, he added.

“This man’s life story holds the key to why he saw his entire existence unraveling, if that’s what occurred, and why he began to question the value of his existing for anyone,” Ablow said.