Manhattan shooting: Horror image shows killer wielding huge gun before slaughtering four

A chilling image has emerged of the Manhattan mass shooter strolling towards an office block while armed with a huge gun moments before he heartlessly killed four people.

The gunman, identified by authorities as Shane Tamura of Las Vegas, entered the New York skyscraper with a rifle and brutally killed at least four innocent people before turning the weapon on himself.The 27-year-old man had travelled more than 2,500 miles to carry out the attack, authorities said.

Surveillance video showed the man exiting a double-parked BMW just before 6.30pm on Monday carrying an M4 rifle, then marching across a public plaza into the building at 345 Park Avenue at 52nd Street in Manhattan, New York City. According to Police Commissioner Jessica Tisch, the gunman started firing shortly after entering the building, opening fire on an NYPD officer. He then shot a woman who was hiding behind a pillar, reports the Mirror US.

READ MORE: New York UPDATES: Didarul Islam among four dead in 'pure evil' mass shooting

READ MORE: New York shooting: New details emerge about Shane Tamura's actions before attack

Follow live updates as much-loved police officer among four dead in 'pure evil' New York mass shooting

The Las Vegas native then made his way to the elevator bank and shot a guard at a security desk and shot another man in the lobby, the commissioner said. He then took the lift to the 33rd floor offices of the company that owned the building, Rudin Management, and shot and killed one person on that floor.

"He then proceeds down a hallway and shoots himself in the chest," Ms Tisch disclosed. A bomb disposal team examined Tamura's car on Park Avenue and declared it free of explosives, she added. The gunman's vehicle, registered under his name in Nevada, was discovered at the crime scene with a rifle case, a revolver, ammunition, magazines, a backpack and medications prescribed to him.

Authorities are now trying to establish the gunman's motive. Ms Tisch told reporters that detectives have established Tamura had a history of mental illness and acted alone. "I cannot speak for any prior law enforcement contact to have had. I cannot, other than to say that, our partners in Las Vegas made us aware of a mental health history. Just two weeks ago," Tisch said during the press conference.

The police officer killed has been identified as Didarul Islam, 36, who had served as a police officer in New York City for three and a half years. “He was doing the job that we asked him to do. He put himself in harm’s way. He made the ultimate sacrifice,” Ms Tisch said. “He died as he lived. A hero.” Officer Islam was an immigrant from Bangladesh who was married and had two young boys.

Jessica Chen told ABC News she was watching a presentation with dozens of other people on the second floor of the building when she “heard multiple shots go off in quick succession from the first floor”. She and others ran into a conference room and barricaded tables against the door. “We were honestly really, really scared,” she said, adding that she texted her parents to tell them that she loves them.

Mayor of New York, Eric Adams, paid tribute to Officer Islam in a heartfelt speech on Monday night, praising him as a "person of faith" who had a deep love for New York City. The mayor continued: "He was doing what he does best, as all members of the police department carry out he was saving lives. He was protecting New Yorkers. He's an immigrant from Bangladesh, and he loved this city, and everyone we spoke with stated he was a person of faith and a person that believed in God and believed in living out the life of a godly person."