Santa Monica Shooter Assembled Gun Himself

It's a chilling scenario that has gun-control advocates reeling. After his attempts to purchase a gun were denied, John Zawahri, the Santa Monica College shooter, assembled a semi-automatic rifle made of parts he obtained separately.

He also purchased ammunition and magazines carrying 30 rounds each, according to Santa Monica police department chief Jacqueline Seabrooks. Other components include an array of realistic-looking replica firearms, several zip guns capable of firing live ammunition, along with an antique black powder firearm converted to a revolver capable of firing .45 ammunition.

Zawahri's rifle appeared to be modified so it could fire more rounds, according to the Los Angeles Times.

Certain types of AR-15-style rifles are banned in California. Officials do not know whether the components were purchased over the Internet, and while the suspect's replicas and gun components were legal, the zip guns and weapon Zawahri ultimately used were not.

Though investigators are still working to determine what triggered the rampage, Seabrooks said officials now know Zawahri led a troubled life and experienced mental health challenges that likely played a role in his decisions to fatally shoot his father and brother then set fire to the family home before going on a 13-minute shooting spree.