A 58-year-old man with a 15-year history of poorly controlled hypertension (BP usually 160–180/100–110 mmHg) presents to the emergency department with sudden-onset severe occipital headache, neck stiffness, and photophobia. His wife reports he was watching television when he suddenly cried out in pain and collapsed. On examination, he is drowsy (GCS 13/15), has a stiff neck, and focal neurological deficits are absent. CT head (non-contrast) shows a hyperdense lesion in the basal ganglia with intraventricular extension. What is the most likely mechanism of this hemorrhage?