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,

Blackstone, one of the world’s largest investment firms, confirmed one of its employees, Wesley LePatner, was among those killed. A Yale graduate, LePatner was a real estate executive, according to Blackstone’s website, and spent more than a decade at Goldman Sachs before joining the firm in 2014.

The last killing of such a scale in the city was during a fast-food restaurant robbery in Queens in 2000. Mass murders of strangers are rare.