New York City is mourning an NYPD officer and three other people killed in Monday's shooting inside an office building in Midtown Manhattan. Officer Didarul Islam was in uniform working as a security guard for a private company at the time of the shooting,

Didarul Islam, 36, was a father of two, with a third on the way, and was working a second job as a security guard at the building where shots rang out.

The attacker reportedly drove cross-country from Las Vegas to New York in the days leading up to the shooting.