A 27-year-old Makaha man pleaded guilty Monday morning to fatally stabbing his neighbor in March during an argument over a drug debt at the Makaha Valley Plantation.

Thomas C. Muscara had been charged with manslaughter and first-degree assault in the death of Johnny Walton Jr., 51, on March 24.

However, under a plea agreement in which Muscara admitted to stabbing Walton, the manslaughter charge was dropped and he was convicted of first-degree assault.

He will be sentenced Nov. 29 by Circuit Judge Karen Ahn.

Initially, police charged Muscara with second-degree murder, but an Oahu grand jury reduced the charges to assault and manslaughter.

Prosecutors had said Muscara started an argument with Walton at the Makaha Valley Plantation condominium complex over a drug debt.

Michael Green, Muscara’s attorney, said during yesterday’s court hearing that after Walton pulled out a knife, Muscara then pulled out his own knife and stabbed Walton in the right arm.

The Honolulu Medical Examiner had said Walton bled to death from a stab wound that severed blood vessels in the right arm.

Police said Muscara admitted stabbing Walton but claimed it was self-defense. He told police that Walton pulled a knife on him and swung it about five times.