NEW YORK (AP) - A former colleague of the doctor who opened fire at a New York City hospital where he used to work says he had been a problematic employee.
 
Dr. David Lazala is a family medicine doctor who said he trained Henry Bello at Bronx Lebanon.
 
Lazala says Bello "was very aggressive, talking loudly, threatening people." He says Bello worked at night as a doctor and sent him a threatening email after Bello was fired.
 
Two law enforcement officials say Bello was allowed to resign in 2015 amid sexual harassment allegations.
 
On Friday, law enforcement officials say Bello walked into Bronx Lebanon Hospital on Friday in a white lab coat concealing an AR-15 assault rifle. One doctor was killed and six other people were injured.