The gunman, who killed a doctor and injured six other people at a New York City hospital a day before, was looking for a physician he blamed for his resignation from the facility, law enforcement sources said.
The shooter was Dr. Henry Bello, a former Bronx-Lebanon physician, who worked there from August 2014 to February 2015 and resigned before he was to be fired, the Guardian quoted hospital spokesman Errol Schneer, as saying.
The slain doctor, Tracy Sin Yee Tam, was on Bronx-Lebanon Hospital Center's 17th floor on Friday afternoon because she was covering for a colleague who needed time off, a hospital official said. She had been working at the hospital close to a year and was very "well-liked by the hospital staff".
Henry Bello then shot himself and staggered into a hallway where he collapsed and died with the rifle at his side, officials said.
Investigators are trying to determine how the gunman got past security and onto the 16th and 17th floors of the 972-bed facility, New York police Commissioner James O'Neill said.
Meanwhile, only one of six people wounded in the shooting remained in critical condition on Saturday, the hospital's vice-president said.