Didarul Islam, a 36-year-old NYPD officer, was off duty and working a security job when he was fatally shot by a gunman who opened fire at the 345 Park Avenue office building on Monday.

Sebije Nelovic always felt safe at 345 Park Avenue. For nearly three decades, she cleaned the ritzy Manhattan skyscraper in one of New York’s toniest neighborhoods. That sense of serenity was shattered by a barrage of gunfire.