NEW YORK (AP) — A portrait of an angry doctor seeking revenge on the medical professionals he believed turned their backs on him emerged Saturday as a New York hospital began to recover from his assault-weapon rampage that left one doctor dead, another critically injured and four staff members and a patient wounded.

Dr. Henry Bello aired his complaints against his former workplace in an email purportedly sent to the New York Daily News about two hours before he returned to Bronx Lebanon Hospital on Friday and pulled an AM-15 assault rifle from under his white lab coat, opening fire before turn...