A doctor who was forced to resign following sexual harassment allegations has shot dead one former colleague and left six other people critically injured at a hospital in New York.
Dr Henry Bello, 45, is said to have threatened to kill colleagues before returning to the Bronx Lebanon Hospital with an AM-15 assault rifle tucked under his white lab coat before opening fire.
Bello then shot himself, and collapsed and died with the rifle at his side, officials said.
Detectives are trying to piece together what prompted Bello to snap two years after he was forced out, and whether he was hunting for someone in particular when he went to the 16th floor of the building - at his previous department - and started shooting.
All six victims are in a critical condition, but are expected to survive. They largely suffered gunshot wounds to the head, chest and abdomen.
The most seriously wounded was shot in the liver, surgeons said.
New York mayor Bill de Blasio said: "There are many, many details that we're still putting together."
He added that terrorism was not involved in the attack.
"This was a horrible situation unfolding in a place that people associated with care and comfort, a situation that came out of nowhere," he said.
Bello's former co-workers described a man who was aggressive, loud and threatening.
"All the time he was a problem," said Dr David Lazala, who trained Bello as a family medicine doctor.
When Bello was forced out in 2015, he sent Dr Lazala an email blaming him for the dismissal.
"We fired him because he was kind of crazy," Dr Maureen Kwankam told the Daily News.
"He promised to come back and kill us then."
The Daily News reported that it had received an email purportedly from Bello about two hours before the rampage.
"This hospital terminated my road to a licensure to practice medicine," the email read.
"First, I was told it was because I always kept to myself. Then it was because of an altercation with a nurse."
He also blamed a doctor for blocking his chances at getting a chance to practice medicine.
People described a chaotic scene as gunfire erupted, spreading terror throughout the medical facility as employees locked themselves inside rooms and patients feared for their lives after hearing an announcement warning of someone in the building with a weapon.
"I thought I was going to die," said Renaldo Del Villar, a patient who was in the third-floor emergency room getting treatment for a lower back injury.
Shortly after receiving a 911 call about an active shooter, police officers went floor by floor, their guns drawn, looking for the gunman. Fifteen minutes later they confirmed he was dead in the building.
Bello may have doused himself with an accelerant and tried to set himself on fire before shooting himself, officials said. Sprinklers extinguished the fire.
Bello had a history of aggressive behaviour. The doctor pleaded guilty to unlawful imprisonment, a misdemeanour, in 2004 after a 23-year-old woman told police Bello grabbed her, lifted her up and carried her off, saying: "You're coming with me."
He was arrested again in 2009 on a charge of unlawful surveillance, after two different women reported he was trying to look up their skirts with a mirror. That case was eventually sealed.
It was not immediately clear if the hospital was aware of his criminal history when he was hired.