NEW YORK - A doctor who lost his job at a New York City hospital opened fire with an assault rifle inside the building on Friday, killing another physician and wounding six other people before taking his own life in a burst of apparent workplace-related violence, officials said.The gunman, wearing a white medical lab coat, stalked two floors of the Bronx-Lebanon Hospital Center, and apparently tried to set himself on fire, officials said. Police found him dead of a self-inflicted gunshot wound as they searched the building, they said.One physician was shot to death, and six other people were injured, five seriously, including one who was shot in the leg, Police Commissioner James O'Neill said at a news conference."One doctor is dead and there are several others who are fighting for their lives right now," Mayor Bill de Blasio told reporters.O'Neill said the gunman was armed with an "assault rifle."The mayor characterized the shooting as an "isolated incident" that appeared to be "workplace-related," saying the gunman was a former employee of the hospital. He said investigators had ruled out terrorism.Neither the mayor nor police immediately identified the suspect or any of his victims.But Bronx Borough President Ruben Diaz told WABC News in an interview that the gunman, Dr. Henry Bello, had been fired by the hospital. Other media reports described Bello as a 45-year-old physician who specialized in family medicine.WNBC television in New York, citing unnamed sources, reported he had resigned from the hospital in 2015 to avoid termination.Details about the carnage were still sketchy. Authorities said the rampage unfolded shortly before 3 p.m. when the gunman went a shooting rampage on the 16th and 17th floors of the hospital.Adding to the pandemonium was a blaze he apparently set, triggering fire alarms that halted elevator service in the hospital, hampering efforts by first responders to reach victims and to evacuate the building.One ambulance worker, Robert Maldonado, told WCBS television in New York that he and his partner were forced to carry a bleeding patient down nine flights of stairs to safety, applying pressure to the man's wound on the way down."Even in the midst of his horror, there were many, many acts of heroism," de Blasio said. "All of the personnel at Bronx-Lebanon Hospital, whose day went from normal to horrifying in a matter of seconds - the doctors the nurses, all the personnel, responded with extraordinary bravery, cool professionalism. They protected each other. They protected their patients."Bronx-Lebanon Hospital Center, about one mile (1.6 km) north of Yankee Stadium, describes itself as the largest voluntary, non-profit health care system serving the South and Central Bronx, as well as among the largest providers of outpatient services in New York City.