Muhammad Youssef Abdulazeez was supposed to appear in court next week for driving under the influence. Instead, authorities are struggling to understand what led him to commit a far more heinous act: the cold-blooded assault that left four marines and a sailor dead and a nation on edge about terrorism.

They've described their search through the remnants of his life as a domestic terrorism investigation — but nothing about his comings and goings had caught their attention before the rampage Thursday morning.

At the scene of the first shooting Monday, in a small strip shopping center in Chattanooga, hundreds of people carried flags outside the military recruiting office where the rampage began.

Several miles away, where five servicemen were fatally shot, yellow police tape still blocked access.