Connor Eckhardt took just one hit of synthetic pot, known as Spice.
Within hours, the California 19-year-old fell into a coma and later died July 15.
On a Facebook page, Connor's family warns that synthetic drugs can take real lives.
"Our son is gone forever from one hit of Spice! Which is legal. How can that be?" the Facebook post said.
While the substance is legal in California, it is banned in Rhode Island, and has been for more than a year.
NBC 10's I-Team confronted employees at the Pawtucket Food Mart in 2012 after a hidden camera investigation found synthetic marijuana and bath salts for sale at stores all over Rhode Island.
But a bill signed into law in July 2013 made the entire class of drugs illegal, and police departments are taking action.
In June, East Greenwich police raided the East Greenwich Farm convenience store. Officers went undercover and found synthetic marijuana for sale, months after it became illegal. Store owner Rakesh Patel is on home confinement as the case against him moves forward.
The Rhode Island Attorney General's Office told NBC 10 that two people are serving time at the Adult Correctional Institutions because of synthetic drugs, and at least 18 other cases are working their way through the legal system.
The change to Rhode Island law means suspects caught with synthetic drugs face prison time just as they would if they were caught with cocaine or heroin.
NBC 10's Cierra Putman spoke with Vinny Florio, who's in recovery after using drugs, including bath salts.
"I had tried it and it's very addicting. It's like it reminded me of like cocaine times 10," he said at the time. "I'm 33. I did a lot of drugs in my life and by far that was the worst drug I ever did."
Eckhardt's mother said she knew her family wasn't the only one suffering because of synthetic drugs.
"So many people have messaged me that their loved ones died too. My son is gone forever. Something hast to be done!!! Please share our story," she posted on Facebook.