Jan 20, 2007 03:00 AM

FRAMINGHAM— Moments after a 15-year-old student was stabbed to death yesterday at Lincoln-Sudbury Regional High School, a 16-year-old classmate blurted out, “I did it. I did it,” to police, a prosecutor said.

John Odgren, 16, of Princeton, pleaded not guilty to first-degree murder in the fatal stabbing of James Alenson, 15, a freshman from Sudbury.

A police report said that after the stabbing, Odgren also said: “Is he OK? I don’t want him to die.”

Authorities would not comment on a possible motive for the stabbing.

Middlesex District Attorney Gerard T. Leone Jr. said a fight broke out about 7:20 a.m. yesterday between Odgren and Alenson in a school bathroom and spilled out into the hallway, where the stabbing took place.

Odgren’s lawyer, Jonathan Shapiro, said Odgren has Asperger’s syndrome, a form of autism, and has been taking medications for many years.

“The defendant has a history of fairly serious psychological diagnoses and has also suffered from hyperactivity dysfunction for many years,” Shapiro said. “What is clear is John has a serious disability.”

Framingham District Court Judge Paul F. Healy Jr. ordered Odgren held without bail. In addition to the murder charge, Odgren was charged with assault and battery with a dangerous weapon, and carrying a dangerous weapon illegally in a school. In first- and second-degree murder cases in Massachusetts, anyone 14 or older is automatically tried as an adult.

Assistant District Attorney Daniel Bennett said Odgren stabbed Alenson twice with a long knife — once in the abdomen and once in the heart. Alenson also had cuts on his neck, Bennett said. The knife was found inside the school bathroom.

Bennett said witnesses saw Odgren leaving the bathroom area.

“The timing of the stabbing strongly suggests that Mr. Odgren planned this premeditated murder and took Mr. Alenson’s life,” Bennett said.

Shapiro requested that Odgren be held in a secure facility at Children’s Hospital in Boston until his next court date, Feb. 2, so his mental competence could be evaluated. Healy denied the request because he did not know whether Children’s Hospital would accept Odgren. The judge said Shapiro could renew his request after checking with the hospital.

Odgren’s parents, Paul and Dorothy, silently consoled each other as they sat in the front row of the courtroom’s seating area and stared at their son, who occasionally looked back toward them. Shapiro said Paul Odgren is a cell biologist doing research at University of Massachusetts Medical School in Worcester. He said Dorothy Odgren is a registered nurse.

No one from Alenson’s family attended the arraignment.

The Odgren family resides in a well-maintained house on Ball Hill Road, a rural residential street in southern Princeton. No one answered the door at the house yesterday afternoon.

Dianna Markley, who lives nearby, described Paul and Dorothy Odgren, John’s parents, as good neighbors whose children were friendly.

“It’s kind of shocking because he’s a good kid,” Ms. Markley said of John Odgren last night. “I feel really bad because they’re really good kids. They’ve all been really polite and gentle boys.”

She said the 16-year-old attended Lincoln-Sudbury because the district offered a behavioral program not available in the Wachusett school district.

“I’m sure the parents are shocked,” Ms. Markley said. “They’ve been great neighbors. They’ve always seemed a really congenial family.”

She said her dealings were more with the children than their parents, because she rides horses and the children would come out to greet her as she rode past.

“They’ve always been very helpful,” she said.

Mrs. Odgren has worked for the Wachusett school district. In a 2003 interview with the Telegram & Gazette about school nursing, she said her duties included counseling students who suffer from anxiety, depression, behavioral disorders and family conflicts.

In the summer of 2005, John Odgren attended a weeklong program on forensics at Mount Wachusett Community College in Gardner. The program was designed to give teens a look at what is entailed in processing a crime scene. A picture of John dusting for fingerprints during the class was published in the Telegram & Gazette with an article about the class.

Yesterday, John Odgren was described by fellow students at Lincoln-Sudbury as a loner who often discussed crimes and evidence-gathering procedures.

Outside the courtroom, Shapiro said, “This is a tragedy for all involved. My client and his family feel for the victim and his family.”

The stabbing stunned Lincoln-Sudbury High students as they reported for school.

Mary Clemens, a 17-year-old senior, said a friend called her yesterday morning on her way to school to tell her the building had been locked down. When she arrived, she saw students gathered in the cafeteria.

“We were told by an administrator that someone was stabbed and it was bad, that that person was taken to the hospital and someone else had been taken to the police,” Clemens said.

“It was shocking,” she said. “You would never expect something like that to happen at our school, but I guess it can happen anywhere.”

All of the school’s approximately 1,600 students were sent home about 10:30 a.m.

“We’re obviously heartbroken dealing with this,” said John Ritchie, the school’s superintendent and principal.

State Education Commissioner David P. Driscoll called the stabbing “everyone’s worst nightmare.”

“The presence of violence in our society today is almost incomprehensible,” Driscoll said in a statement. “It is only made worse when it occurs between young people and impacts the lives of our children. A tragedy of this magnitude defies explanation.”

Matthew Bruun of the Telegram & Gazette staff and Denise Lavoie of The Associated Press contributed to this report.