LANCASTER — A teenager who wrote in his journal about having a compulsion to "kill people" was sentenced Tuesday to life in prison after pleading guilty to fatally stabbing a classmate and the classmate's parents in a middle-of-the-night attack inside their home.

Alec D. Kreider, 17, displayed no remorse and offered no explanation for the grisly murders of Tom and Lisa Haines and their 16-year-old son Kevin, despite emotional statements by family members and the judge's repeated offers to let Kreider speak on his own behalf.

"He is a deviant, cowardly triple murderer," Lancaster County District Attorney Craig Stedman told Judge David Ashworth shortly before he sentenced Kreider to three consecutive life terms without parole — one for each count of first-degree murder to which he pleaded guilty.

Kreider's lawyer described his client as "a child" and urged Ashworth to make the sentences concurrent.

"He's going to spend not only the rest of his childhood behind bars, he's going to spend the rest of his life behind bars," said David Blanck of the county public defender's office. "He knows that."

Kreider, a friend and 10th grade classmate of Kevin Haines at Manheim Township High School, was wearing dark clothing and wielding a hunting knife with a four-inch blade when he entered the victims' suburban Lancaster home through an unlocked door around 2 a.m. on May 12, 2007, Stedman said.

Kreider, who lived with his mother about a 10-minute walk away from the Haines' home, attacked the victims in their bedrooms — first the parents and then Kevin, Stedman said.

Maggie Haines, Kevin's sister and a Bucknell University student who was at home that night, awoke to the sounds of a struggle in Kevin's room and rushed to her parents' room, where her father was lying on the bed and her mother was sitting up. Maggie escaped and ran to a neighbor's home to call the police.

Kevin Haines "put up a significant struggle for his life," but finally succumbed to 11 stab wounds and 15 other cuts, Stedman said. His throat had been ripped out.

The horrific nature of the crime shocked this community in the heart of Pennsylvania Dutch country, and fears that a killer was on the loose became an unwelcome part of life as the police investigation stretched into weeks.

Kreider was finally arrested after he confessed to his father about a month after the murders. He also confessed to a fellow inmate at Lancaster County Prison, where he has been held since his arrest. He has never confessed to police, but their case was buttressed by an assortment of physical evidence, including the murder weapon, shoes that left matching footprints in the home, and DNA.

The judge said he would insert a note in Kreider's file to register his strong objections should Kreider ever be considered for clemency.