(CNN) — During evening rush hour in New York City on Monday, a man calmly walked into a Park Avenue office building lobby and killed a police officer, then opened fire on other innocent strangers.

Officer Didarul Islam, 36, who was guarding the building on a paid security job when he was killed, had served as a police ...

It's a point borne out by recent research from ASIS International, a global organization of security professionals, that showed 14% of companies had no comprehensive plan to address active-assailant ...

A man stalked through a Manhattan office tower firing a rifle, killing four people, including a New York City police officer, ...

Family and friends gathered at Central Synagogue to mourn Wesley LePatner, one of four victims killed in Manhattan office ...

Wesley LePatner, 43, was among the four people killed by a gunman who stormed the Park Avenue building where she worked on ...

There were 23 shell casings and 13 bullet fragments recovered from the lobby of 345 Park Avenue and 24 spent shell casings on ...

Roger Goodell also gave a health update on the league employee who was seriously injured in the gun attack that killed four ...

NEW YORK -- Wesley LePatner, a senior executive at Blackstone, was laid to rest on Thursday. She was one of four killed after ...

Four people, including an off-duty New York City police officer, were killed Monday when a gunman carrying a rifle opened ...

New York City is mourning NYPD Officer Didarul Islam and three other people killed in Monday's shooting inside an office ...

Police Officer Didarul Islam, a father of two with a baby on the way, was one of the four people killed by Shane Tamura ...