Police swarmed Midtown Manhattan on Monday as the mayor of New York City said there was "an active shooter investigation" amid reports a police officer had been struck.

Shane Tamura, 27, who fatally shot four people in the building that houses the National Football League's headquarters Monday, said in a suicide note that he had chronic traumatic encephalopathy, known at CTE,

New York City police detectives searched a studio apartment in Las Vegas that belonged to the suspected gunman in Monday's mass shooting at a Midtown Manhattan.

The gunman in the deadly shooting at a New York City office tower had a background in casino surveillance and once held a private security guard license.

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.