Henry Bello, a disgruntled Nigerian medical doctor, on Friday, barged into the Bronx Lebanon Hospital Centre, New York, United States with an armed rifle, killing one and injuring six others.

According to the New York Police Department, Bello, 45, also opened fire on himself and died in the process.

Bello, was found dead on the 17th floor of the facility, the city police told NBC News.

The gunfire was first reported at 3pm on the eighth floor of the hospital and it was immediately placed on lockdown as police launched a floor-by-floor search for the armed intruder.

“This would appear, preliminarily, to be a former employee dressed in a hospital jacket similar to what you would see a doctor wearing, who is familiar with the hospital, which makes the situation a lot more problematic,” officials said, adding that Bello had a rifle, possibly an AR-15 type assault rifle, and had previously worked at the hospital.

Just before 4pm, the Assistant Commissioner for Communication for the NYPD, Peter Donald, announced the search for the suspect was over.

“One shooter is deceased at the hospital,” he said.

Before killing himself, Bello tried to start a fire on the 16th floor that was doused by the hospital’s sprinkler system, a senior official with direct knowledge of the incident said.

The Federal Bureau of Investigation (FBI) announced in a tweet later that the situation was not an act of terrorism.

There were major warning signs in Bello’s life before the mass shooting, which spanned two floors as Bello opened fire on hospital employees, including other doctors. He had a criminal history.

Dr. Bello had three prior arrests, including one for sexual abuse. The New York Post reported that Bello was arrested in August 2004 in Manhattan “following an incident in which a 23-year-old woman said an assailant grabbed her crotch, held her arms, lifted her up and carried her off, saying, ‘You’re coming with me.’”

Bello was “charged with sex abuse and unlawful imprisonment, sources said. The disposition of the case was unclear,” reported The Post, which added that records against Bello in a 2009 case are sealed.

The gunman also had personal troubles, although they were in the far past. In 2002, Bello was listed as a respondent in a California divorce that listed minor children.

Bello was listed as a family physician on the hospital website. However, despite the fact that Bello is listed as a doctor on the hospital website, The New York Post reported that “there are no state records of a Henry Bello with a medical license.”

A Dr. Henry Bello comes up as a “student in an Organized Health Care Education/Training Program” in the National Provider Identifier Database.

The New York Times reported that Bello had “received a limited permit to practice as an international medical graduate” to gain experience but the permit expired in 2016. He previously had a pharmacy technician license in California, according to the newspaper.