At least one doctor was killed and six other people were injured on Friday when a former doctor of a New York City hospital opened fire inside the building. The gunman later shot himself dead after a failed self-immolation bid, reported Reuters.

The attack took place around 3 pm (local time) on the 16th and 17th floor of the Bronx-Lebanon Hospital Center. Police Commissioner James O’Neill said the gunman, wearing a white medical lab coat, was armed with an assault rifle. He and the other physician were found dead on the 17th floor, while the six others injured were found on the 16th floor, said the police commissioner.

Although the police and Mayor Bill de Blasio are yet to reveal the identity of the gunman, Bronx Borough President Ruben Diaz identified him as Dr Henry Bello. A former family medicine doctor at the hospital, Bello had reportedly resigned in 2015 in lieu of termination after he was accused of sexual harassment, according to The New York Times. A former colleague of the gunman told AP that he was a problematic employee. “[He] was very aggressive, talking loudly, threatening people. All the time he was a problem,” Dr David Lazala told the news agency.

Even as the motive of the attack remains unclear, Mayor Blasio ruled out the terrorism angle and said it was an “isolated incident”. He added that the incident is believed to be “a workplace-related” violence. “This is a horrific situation unfolding in the middle of a place that people associate with care and comfort,” said Blasio, according to Reuters.