NYC is mourning NYPD Officer Didarul Islam and three other people killed in Monday's shooting inside an office building at 345 Park Avenue.

Four people were killed and a fifth was injured in a mass shooting at a Midtown Manhattan office building on Monday.Among those killed was an officer who was a dad of two with a third on the way.Here's what we know about the victims:MORE: Manhattan shooting suspect claimed to have CTE,

An off-duty NYPD officer was among the four people who were shot and killed by a gunman inside a Manhattan skyscraper on Monday, according to the NYPD. Police said Officer Didarul Islam was only 36 years old and a 3-and-a-half-year veteran of the force when 27-year-old Shane Tamura killed him inside