The teen had never injected heroin before, authorities say, and on that hot summer night, she could not find a vein. An acquaintance put the needle in Emylee Lonczak’s arm for her.

As she and others drove back to Northern Virginia from the District, the 16-year-old passed out, court papers say. Someone suggested dumping her in the city, but the other two people in the car said no, the papers say. They finally settled on carrying her into the basement of one of their homes, laying her on a bed.

One friend, who now faces federal criminal charges, later told investigators that he was with the McLean High School student when she died, court papers say. Fearing he would get in trouble, he said, he dragged her body outside and left it near some shrubs. He covered it with a screen window.

About two days later, police found Lonczak’s body. The medical examiner determined that the heroin — combined with a common antihistamine — caused her death.

The incident epitomizes what officials say is a frightening trend. Authorities say more and more people are using heroin, a narcotic with a power they do not fully understand. They use too much — mix it with other drugs — and overdose. Their families are left to ponder what could have been done, as law enforcement officials decide who should be held responsible.

“It’s a growing problem, and I think that law enforcement recognizes it as a growing problem,” said Acting U.S. Attorney Dana Boente, whose office in the Eastern District of Virginia has prosecuted several heroin cases in which users have overdosed. “And it is disturbing.”

The drug seems to be permeating many places across the country. In a news release announcing a bust in New York on Friday, James J. Hunt, acting special agent in charge with the Drug Enforcement Administration, said heroin was “pummeling the northeast, leaving addiction, overdoses and fear in its wake.” In Vermont, the governor devoted much of his State of the State address to discussing heroin and opiate addiction.

And locally, health officials in Maryland warned Friday that heroin tainted with fentanyl, a synthetic opioid, is believed to be responsible for at least 37 deaths from September to now.

The increase in heroin-related overdose deaths is difficult to quantify, because toxicology reports are typically completed months after someone dies.

In Maryland, state health officials said the number of such deaths increased from 245 in 2011 to 378 in 2012. In Virginia, officials said they recorded 91 accidental heroin deaths in the first nine months of 2012, up from 90 for all of 2011 and 70 for 2010. D.C. officials said their statistics are current only through 2011.

The impact is felt most acutely by the friends and families of those who use the drug. Dan Dooley, who coached Lonczak in McLean youth soccer, said he remembered the teen as a quiet, respectful girl who “was shy and almost timid, but she was always trying to get in the game.”

“The only thing I can think is this was a hiccup,” Dooley said. “It’s almost like if she could have avoided it, she would have gone on to a productive life.”

Officials say they are trying to cut the supply of heroin by taking dealers off the streets and temper the demand by explaining how potent and unpredictable the drug is. Many users, they say, are people who became dependent on prescription pain pills but can no longer get them because doctors and pharmacies have reformed how they are doled out.

But heroin, officials say, is a dangerous substitute. Its dosage, they say, is not controlled by the pill, and its purity can vary wildly.

“If you go to heroin, you don’t know who you’re getting it from, what it’s cut with, what quantity can I handle,” said Capt. Nancy Demme of Montgomery County police’s Special Investigations Division. “The results are that you have these overdoses and, in some cases, you have deaths.”

According to a federal affidavit in Lonczak’s death, the teen was part of a group of four who set out from Virginia on Aug. 21 to buy heroin from a dealer in Washington. On the ride back — after someone else injected her — Lonczak fell unconscious, according to the affidavit.

A 20-year-old Virginia man in the vehicle, Kyle Alifom, suggested that the group dump her in Washington, according to the affidavit. The others said no, the affidavit says. Eventually, Alifom and one other person in the group took Lonczak to Alifom’s house in Vienna, according to the affidavit. It says the two took her inside and put her on a bed in the basement.

But after the other person left, Alifom — who was not the one to inject Lonczak — dragged Lonczak’s body to an area filled with shrubs and put a screen window over it, according to the affidavit. He told a detective he believed Lonczak had “died in his presence,” and he was concerned about getting in trouble because he was on probation for other offenses, according to the affidavit. Court records show his probation stemmed from a trespassing charge.

Police found Lonczak’s body about two days later. Months later, Alifom was charged in federal court in Alexandria with knowing that heroin was distributed resulting in a death and assisting the offender to hinder his apprehension, trial and punishment. His defense attorney wrote in court papers that Alifom is accused of being an “accessory after the fact,” noting that Alifom did not sell or give Lonczak any drugs.

The defense attorney, Kevin Brehm, said Friday that Alifom, who is being held without bond, did not suggest dumping Lonczak’s body in Washington during the ride to Virginia. He said his client has cooperated with investigators and was in a residential drug treatment program when he was arrested.

Court papers say Alifom was “struggling” with the rules at the treatment facility — in part because of attention deficit hyperactivity disorder and in part because of Lonczak’s death. The papers suggest Alifom had a long struggle with drug abuse, having completed a drug treatment program at a private boarding school in North Carolina when he was 16 years old.

Officials say that although they are particularly disturbed by the increase in young users of heroin, those who have died after taking the drug come from all walks of life.

In another recent case in federal court in Alexandria, a longtime D.C. heroin dealer who went by the nickname “Shine” admitted his heroin was linked in some way to three separate deaths. One victim was a 23-year-old Army private stationed at Fort Belvoir, another was a 22-year-old Fairfax County woman and the third was a 33-year-old Fairfax County man.

Demme, the Montgomery County police captain, said that the drug has moved to the “forefront” of police’s radar. She said police are trying desperately to convey the message that heroin can be deadly.

“You don't know what you’re getting,” she said. “You don’t know what you’re putting into your body.”

Dan Morse, Alice Crites and Eddy Palanzo contributed to this report.

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