Recurrent fresh rectal bleeding in a 79-year-old man

79-year-old man on apixaban for atrial fibrillation with three episodes of maroon and fresh rectal bleeding over 36 h; haemoglobin 128 → 92 g/L, pulse 96, blood pressure 118/70 after 2 units. CT angiography 8 h ago, during a lull, showed sigmoid and descending colon diverticulosis without contrast extravasation. Colonoscopy was limited by blood. He bled again an hour ago. Request: is he bleeding, and from where?