The New York City Police Department sent detectives to Las Vegas to work with the Bureau of Alcohol, Tobacco and Firearms to execute search warrants and continue the investigation into Monday's deadly shooting inside a Midtown Manhattan office building.

New York City investigators believe a co-worker of the Las Vegas man who killed four, including a police officer, provided a component of the deadly weapon, the 8 News Now Investigators have learned.

A man carrying a rifle killed four people at a New York City office tower Monday, including an off-duty New York City police officer, and wounded a fifth before taking his own life