CENTERVIEW, MO – A Centerview man will spend more than a decade in prison after admitting to fatally shooting his grandfather in 2021, an act he later told authorities was motivated by an unfounded belief that he was being poisoned.
Mastin Paul William Raines, now 23, pleaded guilty Monday to voluntary manslaughter in the killing of his grandfather, 55-year-old William Mark Gustin. A judge sentenced Raines to 13 years in the Missouri Department of Corrections, according to court records.
Authorities responded to a shooting on August 1, 2021, at a residence in the 300 block of Southwest Highway 58 in the village of Centerview, roughly an hour’s drive southeast of Kansas City. Upon their arrival, Johnson County deputies found Raines outside the home. According to police documents, Raines made statements indicating the shooting was deliberate, telling officers at the scene that his grandfather “will never do that again.”
Inside the home, deputies discovered Gustin deceased on the living room floor. Investigators reported that he had suffered gunshot wounds to both the abdomen and neck. Forensic examination indicated the shots were fired from close range, with the bullets passing through Gustin and into the floor below.
Investigators interviewed a witness who was in the home during the incident. The witness told police that they heard gunshots and saw Raines holding a rifle. Fearing for their safety, the witness hid in a bathroom and later persuaded Raines to hand over the firearm.
Raines, who was 19 at the time of the killing, was taken into custody without further incident. During questioning, he told investigators that he believed his grandfather was poisoning him. Raines said he had resolved earlier that day to confront Gustin and had consumed alcohol to muster the courage to follow through with his plan.
Court records show Raines was charged initially with more severe offenses but ultimately reached a plea agreement with prosecutors, resulting in a guilty plea for voluntary manslaughter. No evidence has been presented publicly to substantiate his claims about poisoning.
Gustin, according to his obituary, owned a construction business and was known for his love of the outdoors. His family described him as an avid motorcyclist who enjoyed lake trips and visits to Branson.
The case has drawn attention to mental health challenges and family dynamics underlying violent offenses. Raines will be eligible for parole consideration after serving a portion of his sentence, in accordance with Missouri law.
No additional injuries were reported in the incident, and authorities said the firearm used was secured without further confrontation.