A 16-year-old boy was allegedly decapitated by his classmate.
Lee Manuel Viloria-Paulino disappeared on November 18 never to be seen again.
On Saturday, his classmate was reportedly arrested for his murder.
'This was a horrific, horrific murder,' Essex District Attorney Jonathan Blodgett said at a news conference. 'While it shook the community, we were completely and totally resolved to bring this matter to justice.'
It is alleged that Mathew Borges, 15, stabbed and killed Lee before mutilating his body.
A woman walking her dog on Thursday discovered Lee’s body.
Authorities are unsure of the motive behind the killing.
Mathew pleaded not guilty at his arraignment in Lawrence District Court.
A spokeswoman for the district attorney told PEOPLE: '[Mathew] was ordered held without bail.'