LANCASTER - A Lancaster teen accused of stabbing to death a classmate and the other boy's parents will plead guilty this month, a prosecutor said yesterday.

Lancaster County District Attorney Craig Stedman declined to name the offenses that Alec D. Kreider, 17, is expected to plead guilty to on June 17. As a juvenile defendant, he does not face the death penalty.

"All I can really say for you at this point is, it's on the schedule for a guilty plea," Stedman said.

Kreider is accused of killing 16-year-old Kevin T. Haines and his parents, Thomas A. and Lisa A. Haines, inside their Manheim Township home in May 2007.

The couple's daughter, Bucknell University student Margaret "Maggie" Haines, also was home at the time of the 2 a.m. attack. She was awakened by the commotion, but was unharmed and ran to a neighboring home to summon police.

Authorities have said that Kevin Haines was the intended target, but a motive has not been offered publicly. Both Stedman and a Manheim Township Police spokesman declined to comment about a motive yesterday.

The two boys were sophomores at Manheim Township High School, and Kreider told detectives the day after the slayings that Kevin Haines had been his best friend.

Kevin Haines was a member of the school's German club and quiz bowl team. Thomas Haines, 50, was a salesman; Lisa Haines, 47, taught preschool.

Three and a half weeks after the killings, as police were investigating, Kreider was involuntarily committed to a mental facility after threatening suicide with a gun.

The following week, police said, Kreider confessed to his father, Timothy Kreider, who notified authorities. Alec Kreider was arrested at the mental institution, and later charged with burglary and three counts of criminal homicide.

His lawyer, David L. Blanck, did not return several phone messages yesterday.