Last summer, a narcotics investigator with the Cabarrus County Sheriff's Office took a call from a friend who had noticed teens acting strangely at his neighborhood's pool in Concord.
"I think they're smoking pot," the friend told him.
The investigator, who often works undercover and wants to conceal his identity, was surprised at what he discovered when he arrived on the scene.
"They were 15- and 16-year-olds, and they had heroin at the pool," he said. "And these are well-off kids in a nice neighborhood. A good environment."
Digital Access for only $0.99
For the most comprehensive local coverage, subscribe today.
Drug traffickers have shifted their focus in recent years so that what was once considered a drug used primarily by adults - black tar heroin - now is being marketed almost exclusively to suburban teenagers, experts say.
"Drugs are the epitome of capitalism. It's supply and demand," said Dr. Paul Friday, professor of criminal justice and criminology at UNC Charlotte, and also a resident of Cabarrus County.
"They get the maximum profit from these white, middle-class kids."
A bindle - one hit of heroin - typically costs between $7 and $20 on the street.
Charlotte has been identified as a high-traffic area for black tar heroin, a version of the drug brought in by large Mexican cartels. The city, said Friday, serves as a major source and distribution point for the drug.
Heroin trafficking has become such a problem in Charlotte that the federal Drug Enforcement Administration recently asked Friday to serve as adviser for a new taskforce to deal with the issue of black tar heroin in the area.
Efforts by Mexican cartels to expand into the outskirts of Charlotte are making the drug an increasing problem for surrounding counties, too, Friday said.
"They're just now starting to see black tar heroin move into the affluent areas of Union County, so it's logical they would move into the areas of Cabarrus County as well," he said.
As a result, police in Cabarrus County are seeing a rise in teen use of the drug.
"When I came into vice three years ago, we just started seeing little bits," the Cabarrus investigator said. "Now, it's like the door just opened upon it. The street patrol guys are coming across it on a regular basis."
One of the county's most publicized cases of heroin abuse involves teenager Danielle Holmes.
Last year Holmes, 18, who lived in an affluent neighborhood in Harrisburg, pleaded guilty to second-degree murder and robbery in connection with an alleged heroin buy gone wrong.
She is serving 20 years in prison for the crime.
"She was a beautiful young lady, and you can see what the heroin did to her," said the Cabarrus investigator, who didn't work on the Holmes case.
He said he interviews each of the heroin users he busts.
All of them share the same appearance: sores that look like infected spider bites on their arms, legs, even between toes. Comparing their school pictures to their mugshots shows the startling effects of heroin after just a short time of abuse.
All the addicts arrested told the investigator they started using prescription drugs containing opiates first, before graduating to heroin.
It's a trend, Friday said, that's become common nationwide among teenage heroin users.
"Kids just don't wake up and say, 'Oh, I'm going to go get some heroin,' " he said.
"After they run out of (prescription drugs at) mother's house and grandmother's house and neighbor's house, they've got to have it, and so they go to a distributor. That distributor will move them to black tar heroin."
Signs that heroin and other opiates have taken some hold in Cabarrus County are evident in the number of outpatients seeking help for opiate-related addiction.
The Concord branch of Daymark Recovery Services, a facility that treats substance abuse, reported 268 people received opiate-related services in the county between September and December 2011.
The investigator said the intense high, followed by the extreme sickness if they don't get more of the drug, makes it hard for addicts to stop the cycle of abuse.
"That's one of the bad things about heroin. Out of all the people I've dealt with, I've yet to find somebody that's kicked it."
Part of the solution, Friday said, involves educating teenagers about the pitfalls of addiction before they use.
"Everyone knows you can't law-enforce your way out of a problem like this," he said. "You've got to have prevention programs."
Budget cuts in the past three years within school districts have affected their substance abuse programs.
The Charlotte-Mecklenburg Schools district now has only one substance abuse counselor for every 33,000 students. Union County has one for every 45,000 students. Cabarrus County has one for every students.
Since the cuts in Charlotte-Mecklenburg's program, marijuana use, for example, has jumped higher than the state and national averages, which is no coincidence, Friday said.
"It correlates significantly with the reduction in the prevention programs," he said.
He worries how bad the problem will become before it gets better.
"I've been studying crime for almost 40 years now, and the concern I have the most is the loss of humanness of people when they do this drug," he said. "It has such long-term effects, not only on the kids, but on their siblings, their families."