Dr. Tamara O’Neal spent her final few hours listening to Christmas music and laughing with colleagues at Mercy Hospital and Medical Center. She was one of three people gunned down by her former fiancé at the South Side hospital Monday afternoon. The gunman was also killed; he shot himself after being shot by police. Nurse practitioner Nichelle Bush said the day started like any other — and was going exceptionally well. She and O’Neal worked side-by-side during the doctor’s last shift. “We joked a lot. We laughed a lot,” Bush said. “I remember saying to myself and the charge nurse, ‘I haven’t laughed this much in so long!’ So she had a good day.”