The strongest clue that someone is planning a mass killing, Randall Collins argues, is a ritualized hidden arsenal:
Most of the characteristics of mass killers — low status isolates, bully victims, school failures, gun owners, players of violent games, even persons who talk or write about fantasies of revenge — are far too widespread in the population to accurately predict who will actually perpetrate a massacre. A much stronger clue, I suggest, is amassing an arsenal of weapons, which become the center of an obsessive ritual; the arsenal is not just a practical step towards the massacre, but has a motivating effect that deepens the spiral of clandestine plotting into a private world impervious to normal social restraints and moral feelings.
School shooters and other rampage killers generally amass an arsenal of weapons, bringing far more to the shooting site than they actually use or need. Michael Carneal brought a total of 8 guns, wrapped up in a unwieldy bundle as well as in his backpack: a 30-30 rifle, four .22 caliber rifles, 2 shotguns, and a pistol, and a many boxes of ammunition; but he used only the pistol. The pair of 11- and 13-year old boys who killed 5 and wounded 10 on a school playground in Jonesboro, Arkansas in 1998 carried 7 pistols, 3 rifles, and a large amount of ammunition, of which they fired 30 shots.
The two shooters at Columbine HS carried a semi-automatic handgun, a carbine, two sawed-off shotguns, and almost 100 home-made bombs; they fired 96 shots from the carbine, 55 from the handgun, and 25 from one of the shotguns; their magazines held 240 rounds, of which they still had about 100 rounds, plus 90 of the bombs, when they committed suicide. In the first 20 minutes of their rampage, they killed 13 students and teachers and wounded 21. Then their emotional energy seemed to run out — they even laughed sardonically that the thrill of killing was gone. They left 34 students unharmed out of 56 who were hiding under desks in the school library, and merely taunted other students while they wandered the halls firing aimless shots, before shooting themselves 25 minutes later, synchronizing their last action with a chant: “One, two, three!”
Holmes, the Aurora killer, carried a shotgun, an automated assault rifle, and 2 handguns; previously he spent 4 months amassing equipment in his apartment, including multiple ammunition magazines and 6000 rounds, of which he used only a small part. He also constructed 30 explosives out of aerial fireworks, refilling them with chemicals, a task that must have taken many days.
Brievik had 4 guns, 2 of which he took to the island. He spent two years acquiring the weapons, since guns are hard to get in Europe, and Norwegian regulations are strict. Nevertheless he persevered through the official steps for a hunting license and undergoing training at a police-approved shooting club to get a pistol permit. To create a massive car bomb (which he used in the first phase of his attack, at a government building in Oslo), he spent several years acquiring a remote farm as a front for buying fertilizer and chemicals. He was busy in his hidden backstage, video-game training, writing propaganda, and making a fake police uniform and identification. On the island, he used his police persona to assemble the youths, ostensibly to announce precautions, before starting to shoot them at close range. He brought over 400 rounds with him, fired 186, and still had over half remaining after fatally shooting 67 persons and wounding 33. He too seemed to waver towards the end of his 70-minute shooting spree, making several phone calls offering to give himself up (at 40 minutes and 60 minutes), but then resuming shooting until the police finally arrived.
The stockpile of weapons is symbolic overkill. These guns are for showing off — both to intimidate others, but mainly to impress oneself. They are the sacred objects of the private backstage cult that builds up the rampager’s obsessive motivation to the massacre. Once at the sticking point their emotional energy never seems to carry them far enough to use all their weapons. Whether they bring all their weapons to the massacre or not, their primary significance has been during the build-up; i.e. the guns they bring are from the focus of their cult activities — they are a kind of security blanket.
To be clear about the diagnosis: I am not saying that anyone who collects guns is a potential mass killer. The crucial signs are: first, the guns are kept secret, part of a deep backstage. In contrast, most gun owners are quite open about them; they may be involved in a cult of guns but it is a public cult, visible as a political stance, or a well-advertized pastime such as hunting or target shooting. (Abigail Kohn, Shooters: Myths and Realities of America’s Gun Cultures.) It is the hidden arsenal that is dangerous — psychologically dangerous. Second, the rampage killer amasses a large, unrealistic collection of weapons as far as their actual use is concerned. This symbolic aspect sets them off from other kinds of criminal users of guns.