After a gunman opened fire in a New York City office building and killed four people, experts share strategies for workplaces to implement to mitigate acts of violence.

Then officials say the suspect then got into the elevator and headed to the 33rd floor, the headquarters of Rudin Management.

Police have identified the gunman as Shane Tamura, a 27-year old former high school football player, who authorities say drove from his home in Las Vegas to Manhattan because he believed he had a ...