NEW YORK >> A doctor who appears to have been the intended target of a former physician who started shooting at a New York hospital, killing one person and injuring six, said he has no idea why he would have been singled out.

Dr. Kamran Ahmed told the New York Post he wasn’t the only one Dr. Henry Bello had a problem with.

However, “he never argued with me,” Ahmed said. “I don’t know why he put my name.”

A law enforcement official told The Associated Press that Bello arrived at Bronx Lebanon Hospital in the Bronx on Friday with an assault rifle hidden under his lab coat and asked for a specific doctor whom he blamed for his having to resign. The physician wasn’t there at the time. The official spoke on the condition of anonymity because the person was not authorized to discuss an ongoing investigation.

Ahmed, who specializes in the early detection and treatment of dementia, said Bello “had a problem with almost everybody, so I’m not the only one. That’s why they fired him, because so many people complained.”

Authorities said Bello went to the 16th and 17th floors and started shooting anyway, killing Dr. Tracy Sin-Yee Tam, 32, who, like him, was a family medicine doctor. Hospital officials said that Tam normally worked in one of the hospital’s satellite clinics and was covering a shift in the main hospital as a favor to someone else.

“It makes you think that anything can happen to anybody,” said Tam’s neighbor, Alena Khaim, who saw Tam’s sister outside the home Friday night overcome with grief, shaking and unable to walk. “She was such a sweet girl. You would never think something like that would happen but it happened.”

Before the shooting, Bello sent an email to the New York Daily News, blaming colleagues he said forced him to resign two years earlier.

“This hospital terminated my road to a licensure to practice medicine,” the email said. “First, I was told it was because I always kept to myself. Then it was because of an altercation with a nurse.”

His former co-workers described a man who was aggressive, loud and threatening. Bello had warned his former colleagues when he was forced out in 2015 that he would return someday to kill them.

“All the time he was a problem,” said Dr. David Lazala, who trained Bello. When Bello was forced out in 2015, he sent Lazala an email blaming him for the dismissal.

Of the six others who were injured, one remained in critical condition Saturday and the rest were stable, hospital officials said Saturday. A call Sunday to the hospital for an update was not immediately returned.

Detectives searched the Bronx home where Bello was most recently living and found the box where the gun came from. Investigators were checking serial numbers and trying to determine where it was purchased.