Prosecutors in Massachusetts have alleged that a Lawrence teen murdered and beheaded a classmate in a jealous rage because he thought the victim slept with his girlfriend.

Mathew Borges, who was 15 in 2016 at the time of the crime, was arrested and is now on trial for the brutal murder and dismembering of 16-year-old classmate Lee Manuel Viloria-Paulino, the New York Post reported.

During the hearing in Essex County Superior Court, Assistant DA Jay Gubitose said that investigators discovered that the suspect had texted his girlfriend saying, “I think of killing someone, and I smirk … It’s all I think about every day.”

“The next time you see me, look at my eyes because that’s the last time they’ll be like that. They’ll be dead,” Borges also reportedly texted.

The victim was ultimately discovered on the banks of the Merrimack River missing his hands and head by a man walking his dog early in December of 2016.

The victim’s head was later found discarded nearby.

An investigation showed the victim walking with Borges toward the river on the day he disappeared. Borges told police the two just went to the river to smoke pot.

But police later found a journal entry made by the suspect where he talks of killing Viloria-Paulino and wearing baggies on his feet as a forensic measure.

“The defendant told them he stabbed him to death and cut his head and hands off so he couldn’t be identified,” Gubitose told the court.

Now 17, Borges is being tried as an adult.

Follow Warner Todd Huston on Twitter @warnerthuston.