The only thing more shocking than murder of an entire family in rural Ohio might be to learn how big the area they grew marijuana in is to the international drug trade.

Eight members of the Rhoden family, ranging in age from 16 to 44, were shot to death in four homes early Friday morning, and three of those homes had considerable marijuana operations.

“This is not a plant in a window or six or seven plants in the backyard,” Ohio Attorney General Mike DeWine told a local radio station on Monday. “They were doing this to sell.”

While it’s unclear whether or not the slayings were tied to the cannabis, this region has helped put Ohio in the top 10 of states producing the most marijuana, Russ Baer of the federal Drug Enforcement Administration told The Daily Beast. Last year the state was granted more than half a million dollars for its cannabis eradication program, putting it in the top five of state recipients.

In 2010, the DEA seized 22,000 plants from Pike County and 25,180 plants from neighboring Muskingum. By comparison, the rest of Ohio combined saw 58,000 plants seized that same year. The haul in Pike County was so prolific that authorities burned the contraband on hillsides instead of trying to haul it away.

“Pike County is perfect for a grow operation because you have a lot of notice whether someone’s there and not supposed to be there,” DeWine said. “We have come across in the past in Pike County, on a couple different occasions, some sophisticated commercial grow operations. There was one that made the news [in 2010] where we came across an encampment where we had people in tents who were out there tending the marijuana.”

The eradication program seems to have worked for a while, until $100,000 worth of weed showed up at the local post office this past February.

The Piketon postmaster said the 38-pound package that arrived from California smelled like marijuana so he called the sheriff. When a woman came to pick up the bundle worth $100,000, law enforcement followed her home where they said they discovered a laboratory distilling marijuana into potent hash oil.

“It was obvious that this was not someone doing this for their own recreational use,” the Ohio Bureau of Criminal Investigaton’s Tim Dickerson told the Piketon NewsWatchman in February. “This lab was intended for manufacturing purposes, proven by the type of equipment used, including industrial valves and the very large pipe.” Dickerson said the investigation (still ongoing) also uncovered an indoor grow operation.

“We know a lot of it is moving indoors,” Scott Duff of the Ohio Bureau of Criminal Investigation told local news in 2012. “If you move indoors, you have to control the environment, and that controls how many crops can be produced per year.”

Towns like Piketon are ideal for the illicit marijuana business. Pike County is rural, with less than 30,000 people and fewer cops to stumble upon the sizable chunks of land required to grow weed at the scale needed for commercial use. The growing season there is also longer than average.

“In rural counties generally is where you’re going to see the larger growth,” Jill Del Greco, public information officer for the Ohio Attorney General’s Office, told The Daily Beast. “The landscape is more attractive, better growing conditions.”

Plus, it is strategically located: no more than a six-hour drive from major markets for marijuana like Chicago, Detroit, St. Louis, Indianapolis, Pittsburgh, and Cleveland.

These advantages have even attracted drug cartels from Mexico.

Beginning in 2007, drug organizations like the Sinaola have operated in this part of Ohio, according to Duff. It’s simply easier for cartels to grow, manufacture, and ship marijuana destined for U.S. customers inside the United States instead of having to send the contraband over the border and risk getting caught.

Baer, a 20-year veteran of the DEA, said he’s constantly getting information about Mexican cartels and where they’re located, suggesting that it’s usually in areas where cocaine and heroin are big as well. In a recently declassified document, the DEA outlined the most predominant areas of influence for major Mexican transnational criminal organizations, including the Midwest.

While he can’t comment on the Rhoden case, or whether the DEA has joined investigation, Baer does have experience with the type of marijuana operations that have been discovered in Piketon. As an agent in Tampa, Florida, he spent years learning the ins and outs of the indoor grow market.

“It’s basically a lot of people being paid to babysit the plants,” he says. “They’ll have a couple of rooms in a house with a couple hundred plants and they’re paid to tend them. They won’t derive the revenue, all they do is water them, make sure the irrigation is properly working, and be the point of contact.”

The most effective system for growing indoors is called hydroponic and relies on a specific system of irrigation and nutrients. When effective, it produces cannabis that’s far superior to that grown outdoors—and far more valuable. In recent years, it’s made it difficult for Mexican marijuana to compete with the U.S. market, which could be one explanation for the increased cartel presence.

Despite how benign the job seems, Baer says it’s incredibly dangerous.

“In Tampa I saw two people killed through home invasions,” he says. “The propensity for violence with indoor grows is high.”

Even if the person growing the plants doesn’t own them, they’re still a target.

“You’ve run a risk whatever drug you’re trying to protect,” says Baer. “The cartels wanna make the money and protect the investment. Working as an agent in the field for 20+ years, I’ve seen the toll of the trade for marijuana vendors.”