ABC News

ABC News' Byron Pitts reports:

Cory Monteith, the clean-cut star of the hit TV show "Glee," shocked fans earlier this month when he was found dead in Vancouver of an overdose involving heroin and alcohol - but he has quickly become the new face of the next generation of users of the highly addictive drug.

Though this growing group can be found all over the country - a government study shows 620,000 people admitted to using heroin in 2011, twice the number in 2003 - it's mostly being seen in, of all places, suburbia.

"Every part of Bergen County is touched in some way, shape or form by the heroin epidemic," said Lt. Thomas Dombroski of the Bergen County, N.J., Prosecutor's Office as he drove through the leafy suburbs west of New York City.

Bergen County reported 28 overdoses last year, up from previous years. Most of the victims were younger than 22.

Dombroski said that most parents might not know that, often, the gateway drug could already be in their medicine cabinet.

"Prescription medication is a pathway," he said.

That was the case for Dylan Young, 23, who first spoke with ABC News three years ago when he was still using.

"I started using prescription painkillers that my father had," he said then. "And it went from that."

At 13, Young was smoking pot and drinking. Then he started stealing pills from his parents. Eventually, he moved on to heroin. The hold the drug had on him was so strong that he ended up in rehab six times.

"A lot of us are missing something and then end up filling that void with drugs," Young said. "It can really happen to anyone and it also depends on the choices you make, the people you hang out with. And I just think if you are not staying busy, you might end up using. … When you are in that situation, you usually don't see hope of a life ahead of you. You just see your next fix."

Dombroski said heroin was cheaper than prescription medication, going for $4 a bag compared to $30 for just one 30-milligram oxycodone pill.

Most experts agree that intervention and treatment are key but the irony is that, like Monteith, many heroin addicts die when they start using again right after leaving treatment.

Monteith told Parade magazine in 2011, that, at 19, he'd gone to rehab. And in April, his rep confirmed that he'd entered treatment once again for addiction.

"Most of the overdose deaths that we're getting are people who come back from rehab," Dombroski said. "They get high for the first time since rehab and that high is what kills them."

Young has been clean for three years.

"I just focus on life itself rather than waking up in the morning and thinking about how I am going to get high for the day," he said.