Multiple casualties as gunman opened fire in the lobby of the midtown Manhattan building on Park Avenue that is home to the Blackstone investment firm and other corporations before moving to other floors.

Four people were killed and a fifth was injured in a mass shooting at a Midtown Manhattan office building on Monday.One slain victim worked at Rudin Management -- which is located on the 33rd floor of 345 Park Avenue,

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