Lee Manuel Viloria-Paulino's family knew little about the teen their 16-year-old had brought home in mid-November, except that he was a classmate at Lawrence (Massachusetts) High School.
A few days later, Viloria-Paulino walked out of his grandmother's house and never came back. Worried family members called police and reported the 16-year-old missing.
On Friday came a gruesome discovery: A woman walking her dog found Viloria-Paulino's headless body on the banks of a river, 50km north of Boston.
Mathew Borges, the classmate, was charged with murder two days later. Borges, also 16, will be tried as an adult in the killing, Essex District Attorney Jonathan Blodgett told AP.
Investigators rushed to reassure frightened residents in the Tower Hill community that the killing was not a random attack even as they turned the banks of the Merrimack River into a crime scene.