Adam Lanza shot 20 children and six adults at Sandy Hook Elementary School in Newtown, Conn., using a semiautomatic, military-style assault rifle made by Bushmaster. William Spengler Jr. used the same type of Bushmaster rifle to kill two firefighters last week in Webster, N.Y. The Washington snipers, John Allen Muhammad and Lee Boyd Malvo, also used a Bushmaster in a spree that killed 10 people in 2002.

Bushmasters are by no means the only assault weapons of choice among mass killers (the Aurora shooter used a Smith & Wesson), but the brand’s repeated presence in murderous incidents reflects Bushmaster’s enormous popularity in the gun world, the result of a successful marketing campaign aimed at putting military firepower and machismo in the hands of civilians. Gun owners once talked about the need for personal protection and sport hunting, but out-of-control ad campaigns like Bushmaster’s have replaced revolvers and shotguns with highly lethal paramilitary fantasies.

The guns, some of which come in camouflage and desert khaki, bristle with features useful only to an infantry soldier or a special-forces operative. A flash suppressor on the end of a barrel makes it possible to shoot at night without a blinding flare. Quick-change magazines let troops reload easily. Barrel shrouds allow precise control without fear of burns from a muzzle that grows hot after multiple rounds are fired. But now anyone can own these guns, and millions are in civilian hands.

“There is an allure to this weapon that makes it unusually attractive,” Scott Knight, former chairman of the International Chiefs of Police Firearms Committee, told USA Today, speaking of the Bushmaster rifles. “The way it looks, the way it handles — it screams assault weapon.”