An Arizona man slit the throat of his grandmother Sunday because he was sick of caring for the 81-year-old, police said.

Brandon Smith, 30, was booked on a first-degree premeditated murder charge after his grandmother, Helen Smith, was found dead inside her Chandler house around 3:30 a.m., police said.

Smith allegedly carried out the killing because he was angry about being the only person caring for his grandmother, who suffered from dementia, FOX10 reported. Police said Smith punched the 81-year-old in the face first before deciding “to end her life” when she was unconscious.

Smith grabbed a kitchen knife and slashed his grandmother’s throat while she was in a bathtub, police said.

Police were called to the house and found the grandmother dead. Smith was taken into custody at a nearby location.