How do you murder 150 people for no apparent reason? Lubitz, by early indications, was functional. Lanza wasn’t.
The cockpit voice recorder had co-pilot Lubitz silent and breathing normally right into the crash, while the pilot was banging frantically on the door to the cabin trying to get back in. Lubitz had apparently locked him out.
When did Lubitz decide to do this? The morning of the flight? Last week? A year ago? When he was twelve?
How and when was the moral sense sucked right out of him?