Complex sentence: The terrorist used a.45-caliber handgun in the shooting, in addition he was armed with a 9 mm handgun, a 6-inch knife, and was also carrying extra magazines and ammunition for both guns.
Split into simpler sentences: The terrorist used a.45-caliber handgun in the shooting. In addition, he was armed with a 9 mm handgun, a 6-inch knife, and was also carrying extra magazines and ammunition for both guns.