Massachusetts ? A 15-year-old boy was stabbed to death Friday in a hallway at his high school in an affluent Boston suburb, and a classmate was charged with murder after blurting out, “I did it, I did it,” authorities said.

Investigators would not comment on a motive for the attack.

John Odgren, 16, pleaded not guilty in the killing of 15-year-old James Alenson and was jailed without bail. He was to be tried as an adult.

Odgren’s attorney, 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.”

The two boys got into a fight in a bathroom, and it spilled out into a hallway at Lincoln-Sudbury Regional High in Sudbury, authorities said. Odgren stabbed Alenson twice with a long knife – once in the abdomen and once in the heart, prosecutor Daniel Bennett said.