He handed out Korans? But didn't what he read in the Book of Peace make him think that he shouldn't go through with the massacre?
Or maybe he read that Paradise was guaranteed to those who "kill and are killed" for Allah (9:111), and took that seriously.
Note also that he affected Islamic clothing -- as did another "moderate," Maher Hawash, before the latter embarked upon his jihad.
"Police raid shooting suspect's Killeen apartment," by Victor O'Brien for the Killeen Daily Herald, November 6 (thanks to Ernest):
Bell County SWAT teams barricaded and evacuated a downtown Killeen apartment complex where Maj. Nidal Malik Hasan lived before authorities say he killed 13 people and injured 30 more during a massacre at Fort Hood Thursday....
In the morning, neighbors said Hasan handed Qurans and donated his furniture to anyone who would take it.
Neighbors described Hasan as a quiet man who began wearing "Arabic clothing" in recent weeks. Edward Windsor, a neighbor, never suspected Hasan was in the Army. Hasan's rank surprised Windsor who would never have imagined an officer with a rank of major would have lived in an apartment that rents for $350 and houses soldiers ranked as private first class....