A father who was a serving police officer is among four people who were killed in a shooting attack at an office building in a busy district of New York City.

Didarul Islam, 36, was shot dead while providing security for the site on Park Avenue. Officials said he had migrated to the US from Bangladesh, had two children and was expecting a third with his pregnant wife. He died “a hero”, they said.

Paying tribute to the late officer, New York Mayor Eric Adams said he was “doing what he does best… saving lives. He was protecting New Yorkers”.

Three civilians, two male and one female, were also killed, Adams said. Details about them have not been made public. Another man is in a critical condition.

Suspected lone gunman Shane Tamura, a 27-year-old from Nevada, also died from a self-inflicted gunshot wound, officials said.

He had a “documented mental health history”, and his potential motive is unknown.

Tamura is believed to have shot Islam dead first as he entered the skyscraper at 345 Park Avenue. He went on to attack others, ascending to the building’s 33rd floor before turning his gun on himself.

A post on the New York Police Department (NYPD) account on X said Islam “represented the very best of our department”, and said “he was protecting New Yorkers from danger when his life was tragically cut short today”.

In a press conference on Monday, the city’s Police Commissioner Jessica Tisch said the late officer served in the NYPD’s 47th District, in the Bronx.

She said: “He was doing the job that we asked him to do. He put himself in harm’s way. He made the ultimate sacrifice.” Tisch continued: “He died as he lived – a hero.”

During the conference, Adams said the late officer was “a true-blue New Yorker, not only in a uniform he wore but in his spirit and energy of loving this city”.

The mayor said he had met Islam’s family after the attack, and had expressed his admiration for the late officer, who had served in his job for more than three years.

“This was his dad’s only son,” the mayor reflected. “I think about Jordan, my child, and it is unimaginable to experience a loss of this magnitude.”

Members of Islam’s Bangladeshi community in the Bronx spent Monday evening visiting the late officer’s home, which he shared with his family and parents, the New York Times reported.

They described to the newspaper how Islam had migrated to the US and provided security for a school before becoming a policeman. They said their friend had been an active member of his mosque who had mentored young men in the area.

One of Islam’s mentees, Marjanul Karim, explained why Islam had moved from the school to work in a profession that was seen as less safe. “He wanted to leave behind a legacy for his family, something they could be proud of,” Mr Karim said.