Heated talk about semi-automatic weapons is, relatively speaking, only a somewhat recent development. After being adopted by the army in the 1960s, assault rifles were modified for sale to civilians in the late 1970s, but as late as the mid-’80s, American consumers didn’t express much interest in them. They were pricey and exotic, and to hunters, using a modified army weapon that fired lower caliber bullets than hunting rifles emblemized inefficiency.

Here is how Robert Spitzer, a professor of political science at SUNY Cortland and the author of several books on gun policy, frames the way Americans went from being uninterested in assault weapons to being passionate about them. “There’s no real market for the guns [in the ‘70s]. They’re not selling very well,” he says. “Part of it is that they’re expensive and people aren’t really acquainted with them.” But China’s relations with the United States began to improve around the same time that American manufacturers were introducing these semi-automatic weapons. “In the mid-to-late 1980s, the Chinese dump a lot of cheap, knock-off assault-style weapons on the American market,” Spitzer explains. “The cost is far less and there begins to be an appetite for these weapons.”

Essentially, what happened is that once the market was flooded with knock-offs, appetite for the real thing increased—a pattern not uncommon when it comes to consumer products. Consider the fashion world: According to one MIT study, counterfeits “are often used as ‘trial versions’ of the high-end genuine branded item, with over 40 percent of counterfeit handbag consumers ultimately purchasing the real brand.” Chinese military-style weapons appear to have served as a similar gateway.

“Gun companies are marketing these guns because they are a big moneymaker,” Spitzer says. “They’re huge in terms of profitability. It’s sort of like buying a big fancy automobile, a big pick-up. The mark-up is bigger so there’s more money to be made if you buy a $45,000 pick-up truck than a $19,000 subcompact car that’s stripped down.” Gun companies diversified their products and assault rifles became highly customizable. The AR-15, for example, has been (curiously) monikered by enthusiasts as “Barbie dolls for men” for their ability to be accessorized.

And then, in the ‘90s, tragedy and politics interceded. California passed a first-in-the-nation ban on semi-automatic weapons following a 1989 shooting at an elementary school in Stockton, during which five children were killed and dozens more were injured. A federal ban on assault weapons followed in 1994 (it expired in 2004) as did an embargo on arms and ammunition from China.

But political action wasn’t the only consequence of that 1989 shooting. “After Patrick Edward Purdy opened fire on a school yard in Stockton, California, with an AK-47, sales of the gun and its knock-offs boomed,” Erik Larson reported in The Atlantic in 1993. “Prices quadrupled, to $1,500.” Similar booms in sales have followed for weapons like the AR-15, variations of which were used in the San Bernardino, Newtown, and Aurora shootings.