They are the "angry old men", the "senior shooters", the perpetrators of "grey rage" - call them what you like. But in the week that the United States commemorated the first anniversary of its most murderous school shootings, at Columbine High School in Colorado, another scourge loomed: it was pensioners who were toting guns to deadly effect.
A total of four people were killed and nine injured in two shootings at housing complexes for the elderly. To call them old-age homes would be a misnomer: the first was Lincoln Park Senior Tower, a high-rise block in a suburb of Detroit occupied by lower-income pensioners. The second was on the other side of the country at Ventana Lakes near Peoria in Arizona, the sort of landscaped complex of detached houses, tennis courts, swimming pools and clubhouses much favoured by middle- and upper-income Americans when they retire.
Aside from geography and economics, however, the two incidents had much in common. In Lincoln Park, Ken Miller, 56, was threatened with eviction after accusations from residents that he used bad language. On Tuesday, after several warnings, he was called to a meeting with the administrator to be given notice to quit. Reports said that he stormed out of the meeting saying: "You're not going to assassinate my character and you haven't heard the last from me."
He returned later with a rifle, firing at his accusers and anyone else who got in the way. Two elderly women were killed and six other people were taken to hospital. After rampaging through the building, he was found locked in a flat, suffering the effects of an overdose of painkillers. His son said that his father had been adamant that the charges against him were unfounded and that he was the victim of a vendetta.
At Ventana Lakes, the pensioner gunman was Richard Glassel, 61, who had been engaged in something akin to a running battle with the management on the subject of landscaping. Glassel, fellow residents said, wanted the bushes around his house to be allowed to grow full and luxuriant. The estate rules, though, dictated that they be cut back. "He ordered the landscape committee not to take care of his yard, and you're not allowed to do that," a fellow resident said, noting that Glassel would have signed up to the rules before he moved into his house.
Over the past year, Glassel had apparently defaulted on his mortgage, and the house had been repossessed. But before he left, he had comprehensively vandalised it inside, sawing the bath and kitchen cabinets, cutting the wiring, and removing appliances. Residents said that they had not seen him for months when he suddenly turned up again last week, stormed into a meeting of the residents' association and opened fire with a rifle and two handguns. Two women were killed and three others injured. He was stopped only when his rifle jammed and half a dozen residents tackled him.
In both cases, the gunmen were white, suburban and hitherto law-abiding citizens who seem to have stored up their anger for years before they finally snapped. But they were also known to turn to anger quickly and were viewed by their peers as anti-social misfits - just like their much younger counterparts in the rash of school shootings. The availability of firearms made their rage deadly.
In both cases, too, what they were railing against was the pressure applied by their peers to conform. To be sure, they had signed up to the rules and the majority clearly complied. But the pettiness of rules that allowed a dirty joke or a preference for shaggy bushes to be grounds for eviction is predicated on the communities being completely homogeneous or run as mini-dictatorships.
The trend for Americans, especially older white Americans, to move into private estates cuts them off from the diversity of life outside. Often called "adult" communities, these blocks or estates are restricted by age to the point of excluding all children, except as very temporary visitors.
They set income requirements that have the effect of excluding those of a different economic group. And the disparity in life expectancy means that men find themselves, perhaps for the first time, in a minority - and one that is organised and led by women.
For many residents, this is the first time they have ever had leisure on their hands and they apply the same zeal for organisation to their retirement that they applied to their working lives. There are classes and committees and participation is expected. Space for the loner is limited.
As the baby-boomers start to collect their pensions, simple demography dictates that there will be more and more angry old men to vent their resentment. "Grey rage" is at hand.