Gunman with assault rifle opens fire inside New York skyscraper, killing four before turning weapon on himself"

 A gunman seen carrying an M4 assault rifle killed four people, including a police officer, when he opened fire in broad daylight in the heart of New York City, before taking his own life.

In terrifying security camera photos, the gunman could be seen striding into a midtown Manhattan office building on Monday wearing a sport coat and button-down shirt while openly carrying the large rifle by his side. 

The gunman was identified as 27-year-old Shane Tamura from Las Vegas. 

A former high school football player with a history of mental health issues, the gunman had traveled across the country in the days leading up to the shooting, according to NYPD Commissioner Jessica Tisch. 

It was also revealed that the gunman had recently been fired as a security guard at a casino in Las Vegas. 

The building he targeted houses Blackstone asset management and the NFL. 

Tamura had a silencer on his rifle when he opened fire inside the lobby at around 6.30pm, according to CNN. The firearm also had a scope and strap. 

NYPD officer Didarul Islam, 36, who had been on the force for three years was working private security at the time on his day off, and was shot and killed in the lobby of the building. 

The man went to the elevator bank and shot a security guard who was taking cover behind a security desk and also another man in the lobby, Tisch said. 

The man took the elevator to the 33rd floor to a real estate management company and one person was shot and killed on that floor. The man then walked down a hallway and shot himself, she said.