The best armed mass shooters?

Obviously Stephen Paddock comes to mind almost immediately; he had twenty-three rifles of mostly AR-and-AK-style as well as the .38 caliber pistol he shot himself with. All the rifles were heavily modified.

Michael McLendon was armed with an SKS and a Bushmaster AR-15 type rifle as well as "at least one" .38-caliber pistol.

Charles Whitman of course had his veritable arsenal that is too long to accurately, confidently type from memory.

Woo Bum-kon was pretty well-heeled.

Richard Farley had 7 guns, a foot long Knife, a smoke bomb and a bulletproof vest during his shooting.

I've always liked Michael Ryan's weapons, a Type 56 Semi-Automatic Rifle, an M1 Carbine and a Beretta 9FS Pistol, how he managed to kill 16 people with all three of them combined in a wide open area is pretty impressive.

James Holmes with his AR-15, remington 870, 2 .40 caliber glocks, tear gas, his wealth of protective gear and all of his homemade explosives (intended for cops but still)

Joseph M Harris had a bulletproof vest,a gas mask, and he was armed with a 9mm Uzi handgun, a .22-caliber machine gun with a silencer, a samurai sword, three hand grenades, and some other homemade explosives

Vic Lee Boutwell had full body armor, two "assault rifles" and three pistols, and was carrying about 1,000 rounds of ammunition

Joeseph Wesbecker had a Polytech AK-47S, (a Chinese-made semiautomatic AK-47 derivative), a SIG Sauer P226 9mm pistol, and a duffel bag containing two MAC-11s, a snubnosed .38 caliber Smith & Wesson Model 12 Airweight revolver and a bayonet

Anders Breivik with his Mini-14 (with a holographic sight, dual flashlights, bayonet and verticle foregrip), Glock 34, ANFO bomb and full body armour

Dmitry Vinogradov with his body armour, vepr-12 semi-automatic shotgun and Benelli m3 pump-action shotgun

Alvin Lee King had a M1 carbine with a heat shield and bayonet, a Colt AR-15 SP1 with telescopic sight and bayonet, Smith & Wesson M10 .38-caliber revolver  and a Röhm RG-10 .22-caliber revolver

And while he only managed 3 kills (including himself) Zachary Brimhall had 10 various nonspecified guns in his car and used an AK-SAR-1 rifle and a .44 magnum revolver.

Others I can also think of who were heavily armed but had less than those listed
James Huberty
David Malcolm Gray
Denis Lortie
Martin Bryant
Julian Knight

Anders Breivik: Mini-14 said to have ten 30-round magazines and Glock 34 that had six magazines in total 4 of which where 30-round magazines.

Adam Lanza: Bushmaster XM-15 Rifle with ten 30-round magazines as well, the two pistols in total had twelve magazines with six each per pistol, he almost had 500 rounds of ammunition when he entered the school and that's the weapons he ended up bring in, there were several weapons including the Saiga shotgun that he left in his car which he had plenty of ammo for lying about in his house.

John Zawahri had an AR15 with fourty 30 round clips and a Remington 1858 revolver with another 100 round as his secondary weapon

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I find that Alois Huber was well armed, although I not know how much ammo he had