Hawaii island police arrested a 21-year-old man on suspicion of first-degree murder in connection with the double homicide of his grandparents in Hilo today.

South Hilo patrol officers responded to a call of an unknown disturbance at a Makalika Street residence shortly before 7 a.m.

Upon arrival, officers determined two residents with stab wounds were dead.

They were identified as Jeffrey Yoshio Takamine and Carla Kayoko Takamine, both 68, of Hilo, the Hawaii Police Department said.

Autopsies will be performed Tuesday to determine the exact cause of death.

Police said a 28-year-old man at the residence sustained multiple lacerations to his head. He was taken by ambulance to Hilo Medical Center where he was treated and released.

Police said the suspect, identified by police as Joshua Ho, was being restrained by family members at the residence until police arrived and arrested him on suspicion of first-degree murder.

He was taken to a hospital for lacerations to his hands before being transferred to a police cellblock in Hilo.

Detectives of the Area I Criminal Investigation Section are investigating.

Jeffrey and Carla Takamine owned Big Island Delights, a cookie and confections company that opened in 1996. The business later expanded its product line to locally grown coffee, crispy bagel chips, gift baskets and other goodies, the company’s website said.