A 75-year-old man with no significant medical history presents to the emergency department with recurrent bright red blood per rectum. Previous workup included computed tomography angiography (CTA), upper endoscopy, and anoscopy, which were all negative. Previous colonoscopy showed pancolonic diverticulosis with blood throughout the colon. He is now receiving his fifth unit of packed red blood cells. His blood pressure remains 80/50 mmHg despite resuscitation. What is the best next step in this patient’s management?