An employee of the NFL was left seriously injured after a shooting occurred in New York  City on Monday, according to league commissioner Roger Goodell.

ESPN reported that Goodell sent a memo to relay the unfortunate news. The incident happened at a midtown building in Manhattan, which houses the NFL's offices and several financial companies.

It added that four people, including an off-duty police officer, were killed, while another person was “critically wounded.”

Goodell said the employee, who was rushed to the hospital, is now in stable condition.

“NFL staff are at the hospital and we are supporting his family. We believe that all of our employees are otherwise safe and accounted for, and the building has nearly been cleared,” said Goodell in the memo, as quoted by ESPN.

The suspect was identified as Shane Devon, a 27-year-old resident of Las Vegas. After opening fire, he was found dead from “what is believed to be a self-inflicted gunshot wound,” according to ABC News. New York Police Department (NYPD) commissioner Jessica Tisch said Devon was a “lone shooter,” based on their initial probe.

Goodell assured in the memo that “increased security presence” will be deployed in the NFL's offices in the coming weeks to ensure everyone's safety.

“Every one of you is a valued member of the NFL family. We will get through this together,” added the 66-year-old Goodell.

In a separate report, ESPN identified the murdered police officer as Didarul Islam, a 36-year-old immigrant from Bangladesh. His wife is pregnant with their third child.

ESPN also detailed the suspect's moves before the shooting: “Surveillance video showed a man exiting a double-parked BMW and carrying an M4 rifle before he walked toward the building. He immediately opened fire on the NYPD officer as he entered the building and shot a woman who tried to take cover. He then began ‘spraying' the lobby with gunfire, Tisch said.”

The NYPD is still investigating the motive of the suspect, who reportedly had mental health issues.