Unarmed troops scrambled to get away from Chattanooga gunman as he blasted through building

It took only three to five minutes for a Chattanooga gunman to blast his way through a Navy-Marine reserve center on the banks of the Tennessee River, killing four Marines and mortally wounding a sailor.

In the most detailed account so far of last Thursday's shooting rampage, officials described how Muhammad Youssef Abdulazeez crashed through the gate and entered the building shooting.

The 20 Marines and two Navy corpsmen at the center were mostly unarmed and had no choice but to try to escape as Abdulazeez approached with an assault rifle, a handgun and a vest full of extra ammunition.

Abdulazeez mortally wounded one sailor as he entered the building and killed four Marines in a gated motor pool area. That's when Chattanooga police arrived. They killed Abdulazeez, but not before he wounded one of them.