A Missouri resident is facing a prison sentence after fatally shooting his grandfather, asserting that the victim had been poisoning him. He later remarked to police that the grandfather “will never do it again.”

At the age of 19, Mastin Paul William Raines took the life of his 55-year-old grandfather, William Mark Gustin, back in 2021. Now 23, Raines has admitted to voluntary manslaughter and received a 13-year prison term, as documented in court records.

According to an arrest affidavit cited by the Warrensburg Star Journal, deputies from the Johnson County Sheriff’s Office responded to reports of gunfire on August 1, 2021. The incident took place at a residence located on the 300 block of Southwest Highway 58 in Centerview, a village roughly 55 miles southeast of Kansas City.

Upon arriving, deputies encountered Raines, who allegedly stated, “He will never do it again,” according to the affidavit. When asked to clarify, Raines reportedly added, “My grandfather, he’ll never do that again.”

Officers discovered Gustin deceased on the living room floor, with gunshot wounds to his stomach and neck, indicating that Raines had fired at close range. The bullets penetrated the victim and continued into the floor.

A witness recounted to investigators hearing gunshots and seeing Raines holding a rifle. The witness sought refuge in a bathroom and eventually persuaded Raines to relinquish the weapon.

After receiving his Miranda rights, Raines reportedly accused his grandfather of poisoning him. He allegedly said that he decided that “Today was the day” and loaded the firearm and began drinking alcohol to gather up the courage to shoot him.

According to his obituary, Gustin owned a construction company.

“He enjoyed spending time in the outdoors, trips to the lake and going to Branson; he especially enjoyed riding his motorcycle,” the obituary said.