PLANO (CBSDFW.COM) – K2, the controversial form of synthetic marijuana that sparked outrage among parents and lawmakers during the last legislative session, is back in the news as a North Texas doctor prepares a study linking the briefly-legal drug to heart attacks in teens.

Kim Tate was one of the first parents to write Sen. Florence Shapiro (R – Plano) asking her to present a bill banning the substance. She says she believes it killed her son.

“He was my world. All I have is memories now,” said Kim Tate.

Tate’s son Dominique was, by all accounts, a healthy 19-year-old. He died suddenly on August 6, 2010, two months, his mother says, after he started using K2.

“I still think it’s the K2 that took his life. I do,” she said.

K2 was marketed as potpourri, but had been sprayed with a substance chemically similar to marijuana. The packaging, often colorful and psychedelic, had small notices saying it was “not for human consumption.”

Despite the slim warning, it became popular among teens and adults looking for a legal high that wouldn’t show up on drug tests.

Tate started researching the product after she buried her son. But an autopsy didn’t find any traces of K2 in her son, only traces of marijuana.

But again, experts say K2 goes undetected on drug tests.

Most alarming to Tate was what the Medical Examiner told her: “That he had an enlarged heart,” she said.

“And that she said the valves to the heart, she could tell they were damaged.”

Experts don’t know if K2 caused Dominique’s death or even contributed to it. They do know it contributed to heart attacks in three 16-year-old North Texas area boys, all of whom survived.

“One hypothesis is something in the K2, one of the chemicals, caused the coronary arteries to spasm and close off temporarily. That caused a blockage of blood flow to the heart muscle,” said Dr. Colin Kane.

Kane, a cardiologist with University of Texas Southwestern and Children’s Medical Center, is one of the researchers publishing a study linking K2 and heart attacks in teenagers.

“It was suspicious for us enough and important to get the word out,” Kane said.

Texas banned K2 in September. But, some smoke shops are still selling similar products in kid-friendly packets and flavors.

Clerks are careful how they sell it.

“Technically, you’re supposed to just burn it and let it fill the room,” one said, captured by a CBS 11 hidden camera.

A slew of YouTube videos show teens smoking the substance. Some are coined “Comatose Candy.”

“The common thread is that it contains some sort of synthetic version of marijuana. We just don’t know everything about it yet,” Kane said.

Tate only knows it could be why her only son is gone.

“It’s been really hard. It’s been really hard,” she said.

Last month, two convenience store clerks in Hood County were arrested for selling K2 at the tobacco shop where they worked.

Guravtar Singh, 28, and Vicki Buckner, 43, were each charged with manufacturing and delivering a controlled substance. Authorities say additional charges are pending.