While a parent sat upstairs, a group of teenagers partying in the basement of a Fairfax County home in February crowded into a bathroom to crush and snort prescription drugs, a prosecutor said Monday.

David Evers, an 18-year-old senior at Centreville High School who was headed to college, traded a morphine pill to his classmate Alexia Springer, 17, a homecoming princess and varsity runner, for an oxycodone, the prosecutor said.

The drugs were two of a handful Springer ingested that night that would ultimately lead to her death.

Evers pleaded guilty in Fairfax County court Monday to supplying the morphine to Springer, a case that cost one student her life and another his future and highlighted the dangers of teenagers abusing prescription medication.

[Teen arrested for supplying drug that killed classmate]

David Evers (Fairfax County Police)

Virginia Assistant Attorney General Marc J. Birnbaum said in court that Evers had become known as the “Boof man” at Centreville High School because he had begun distributing prescription drugs to fellow students on a handful of occasions — even apparently as he was accepted to more than one college.

“This is not an isolated incident,” Birnbaum said of the events that led to Springer’s death. “This is not something that just happened on this one day. This is something that happened throughout the school year.”

Birnbaum said Springer, a junior, probably had taken a Xanax before the party on Feb. 29. Prosecutors said about 20 to 30 students from Centreville and other schools attended the party at a Clifton home that was not identified.

Birnbaum said Evers and Springer, along with five or so other partygoers, slipped into the basement bathroom for 20 to 30 minutes to trade the pills and snort the drugs. In court, Birnbaum declined to disclose Evers’s morphine supplier.

Rona Powell, Springer’s mother, said in a May interview that her daughter also drank at the party. Powell said her daughter went home after the party. She texted and went online, but never woke up after going to sleep that night.

One of Springer’s friends, who had spent the night, found her unresponsive the next morning and alerted authorities.

The medical examiner ruled that Springer’s death was accidental and the result of a combination of alcohol, morphine, Xanax and oxycodone. Springer’s family declined to comment after Monday’s hearing.

“She was a really good kid,” Powell said in May. “This is something I would never have thought would happen to her.”

Evers’s family also declined to comment, but his attorney Christie A. Leary said in court that he had been suicidal and depressed since Springer’s death.

“Before this, he had a wonderful future ahead of him,” she said of her client. “Those plans have been derailed.”

During the hearing, Evers spoke only to answer questions from Circuit Judge Randy I. Bellows.

Leary argued that Evers should remain out on bond before his Dec. 2 sentencing, but Bellows disagreed, saying the defendant’s misdeeds “were catastrophic.”

“A child died,” Bellows said before Evers was handcuffed and led to jail.