Walter Wallace Jr.’s family says they called for an ambulance on Monday afternoon because the 27-year-old was in the midst of a mental health crisis. Police arrived instead, and Wallace was shot and killed by two officers. Only three weeks earlier, the department announced a new program calling for a clinically trained behavioral health worker to help identify 911 calls that require a different kind of response. WHYY reporters Ximena Conde and Nina Feldman explain why that initiative wasn’t implemented in time, potentially costing Wallace his life.