the gunman taking aim at an e.r. doctor, his ex-fiancee, and then going on a rampage, targeting an officer and a pharmacist who just happened to be getting off an elevator. abc's alex perez in chicago again tonight. >> reporter: tonight, the horrifying new details about the deadly rampage at mercy hospital in chicago. >> holy [ bleep ]! >> reporter: authorities say 32-year-old juan lopez arrived just before 3:30 monday afternoon to confront his ex-fiancee, e.r. doctor tamara o'neal, demanding his engagement ring back. that's when police say lopez shot and killed her. lopez then moving inside the hospital, killing chicago police officer samuel jimenez and pharmacy technician dayna less. >> i need officers to go to the lobby. there's a female shot in the lobby. >> that poor woman had gotten off of an elevator, had nothing to do with nothing, and he shot her. >> reporter: police heroically facing off with the gunman as doctors fled with patients. one officer struck in his holster.