Columbine, 10 years later

Clips, Tec9, and sawed-off shotgun used in the attacks.

Wiki:

In the months prior to the attacks, Harris and Klebold acquired two 9 mm firearms and two 12-gauge shotguns. A rifle and the two shotguns were bought by a friend, Robyn Anderson, at a gun show in December, 1998.^[40] Harris and Klebold later bought a handgun from another friend, Mark Manes, for $500. Manes was jailed after the massacre for selling a handgun to a minor,^[41] as was Philip Duran, who had introduced the duo to Manes.^[42]
With instructions from the Internet, they also built 99 improvised explosive devices of various designs and sizes. They also sawed the barrels and butts off their shotguns in order to make them easier to conceal.^[4] The two perpetrators committed numerous felony violations of state and federal law, including the National Firearms Act and the Gun Control Act of 1968, even before the massacre began.
Harris carried a 12 gauge Savage-Springfield 67H pump-action shotgun (serial no. A232432) and a Hi-Point 995 Carbine 9 mm semi-automatic rifle with thirteen 10-round magazines, fired 96 times. Harris's other weapon, the shotgun, was fired a total of 25 times. Harris committed suicide by shooting himself in the head with his shotgun.
Klebold carried a 9 mm Intratec Tec-9 semi-automatic handgun manufactured by Navegar, Inc. with one 52-, one 32-, and one 28-round magazine. He also carried a 12 gauge Stevens 311D double barreled sawed-off shotgun (serial no. A077513). Klebold's primary weapon was the Tec-9 handgun, which was fired a total of 55 times. Klebold would later commit suicide via a shot to the left temple with the Tec-9.

Eric Harris and Dylan Klebold caught on the high school's security cameras in the cafeteria shortly before committing suicide