Andreas Lubitz, the co-pilot who is believed to have downed a Germanwings plane last week, researched suicide methods and information on how cockpit doors worked before the crash, ABC News reported Thursday. Investigators also said the second black box was unearthed from the wreckage in the French Alps after nine days of searching. The voice recorder is currently being examined.

The box could reveal more clues behind the March 24 disaster, which killed all 150 people aboard Flight 9525. The first black box, which was found last week, captured the last moments of Flight 9525 with the captain yelling at his co-pilot Lubitz to “open the goddamn door.” Lubitz’s breathing was recorded by the black box with the chilling screams of the passengers in the background before the plane hit the ground at 10:40 a.m., the Mirror reported.

Prosecutors said Lubitz had been treated for “suicidal tendencies” years before, and that he “deliberately” plunged the commercial jet into the Alps, about 100 miles north of Nice. Authorities have not found a suicide note nor any other sign from Lubitz claiming responsibility for the crash.