As the investigation into the fatal shooting of a health care executive in Manhattan enters its fourth day, police are piecing together clues, including a backpack, photos, video, ammunition, DNA and more, to help zero in on a suspect they believe is no longer in the city. The shooting suspect, believed to have left New York City on an interstate bus, has not been identified or located NYPD officials told CNN. Learn more about your ad choices. Visit podcastchoices.com/adchoices