Lee Manuel Viloria-Paulino, 16, was found slain on the banks of the Merrimack River in Lawrence. (Facebook)

Cops in Massachusetts arrested a 16-year-old boy accused of decapitating his classmate whose disappearance was reported to police in mid-November.

A woman walking her dog along the Merrimack River discovered a body later identified as missing Lawrence High School sophomore Lee Manuel Viloria-Paulino, 16, along the shore on Thursday afternoon.

The body was in a gruesome state — the arms had been hacked off and the head was found 50 feet away, according to the Eagle Tribune.

Viloria-Paulino’s classmate Mathew Borges was arrested Saturday morning after investigators found evidence at his home and along the river linking him to the teenager’s death.

The Boston Globe reports Mathew visited Viloria-Paulino’s home once before his disappearance on Nov. 18.

Viloria-Paulio’s family filed a missing person’s report, fearing the worst, but heartbroken relatives said police ignored the case.

“We are poor, we are Hispanic, they considered this a normal runaway case,” the teen’s grandmother, Ivelisse Cornielle, told the Boston Globe. “I told them from day one that it wasn’t.

Cornielle wonders if her grandson would still be alive had police taken Viloria’s disappearance seriously — sooner.

“It’s my pain,” she wailed at a press conference.

Essex District Attorney Jonathan Blodgett said Borges will be arraigned on Monday and charged as an adult.

“This was a horrific, horrific murder,” Blodgett said. “While it shook the community, we were completely and totally committed in our resolve to bring this to justice.”