A 19-year-old man from St. Cloud acknowledged quietly in court Monday that his drug dealing was responsible for the overdose death of a promising Woodbury High School honor student last winter.

Alexander Lee Claussen pleaded guilty in Washington County District Court in Stillwater to third-degree murder for selling a synthetic drug, marketed as LSD, that killed 17-year-old Tara Fitzgerald on Jan. 11, just hours after she took it.

Claussen is the second of five teenagers who prosecutors say were part of a county drug-dealing chain to plead guilty in the case. Last month, the 19-year-old to whom Claussen sold the fatal drug, Cole A. Matenaer, of Woodbury, pleaded guilty to third-degree murder.

Claussen, Matenaer and three 17-year-olds from Woodbury were charged in May in what County Attorney Pete Orput described as a chain of drug sales. Claussen was implicated as a distributor, selling drugs out of his house in St. Cloud.

Last month, in a related court action, Claussen was charged in Stearns County with first-degree sale of a synthetic drug exceeding 50 grams in weight. He also was charged with fourth-degree sale of a hallucinogen.

In that case, Claussen sold drugs in April to a confidential informant in a "controlled buy," the criminal complaint said. "A subsequent search of the defendant's vehicle and home produced approximately 305 dosage units of synthetic acid," the charges said.

On Monday, Claussen was brought from the jail into district court, where he admitted that he supplied the drug that killed Fitzgerald.

"You sold a substance that went through the chain and ended up in her mouth?" asked defense attorney Michael Brandt.

"Yes," Claussen said softly.

"Simply put, you were a drug dealer, is that true?"

Claussen acknowledged that he had sold marijuana and cocaine, as well as synthetic drugs that he bought for $1.70 a dose from a source in Minneapolis.

He also acknowledged evidence that the synthetic drug, 25i-NBOMe, that killed Fitzgerald in an overdose at her house during a sleepover with a friend had come from him.

The drug was marketed as LSD, the charges said.

Fitzgerald and her friend each placed a dose on their tongues for 20 minutes and then swallowed it. Police later found that the girls' cellphones contained videos of them under the influence of the drug.

Emergency responders were dispatched to Fitzgerald's home the morning of Jan. 11 because she "was not breathing and was unresponsive after reportedly experimenting with a substance similar to LSD," the charges said.

She was pronounced dead after her arrival at Regions Hospital in St. Paul.

The criminal complaint also said the drug was packaged in a tinfoil wrapper that contained two small square pieces of paper, or "tabs," that were light pink in color.

Claussen, who turns 20 on Friday, told Judge Richard Illka on Monday that he sold that drug to Matenaer. Claussen didn't know where the drug went from there until a criminal investigation uncovered links in the distribution chain, according to court testimony.

Fitzgerald was a Woodbury High School junior and an honor student. She read several books at a time and enjoyed softball, skateboarding, the Beatles and Coldplay. She also was proud of her Vietnamese and Irish Catholic backgrounds.

Claussen's "straight plea" on the murder charge — a crime related to the distribution of dangerous drugs — means there was no agreement with prosecutors. Illka will decide at a Jan. 23 sentencing how much time Claussen might spend in prison. State guidelines recommend a range of 74 to 102 months for third-degree murder.

Prosecutor Imran Ali said "overwhelming evidence," much of it in recovered text messages, led to Claussen's guilty plea.

An investigative report that includes those text messages and witness statements will remain confidential, Illka said.

The judge said he would release Claussen from jail on Tuesday to attend chemical dependency treatment in East Grand Forks, Minn. Should he fail in the program, he must report back to the jail, Illka said.

Also charged in May were Sydney C. Johnson, Alistair C. Berg and Brian P. Norlander, all Woodbury teenagers. Hearings to determined whether they will be certified as adults in court proceedings will be held this fall.