The NYPD told the New York Times investigators are looking into the possibility the gunman who killed UnitedHealthcare CEO Brian Thompson may have used what is known as a veterinary gun, a larger firearm used on farms and ranches. Also Friday, a backpack believed to belong to the suspect was found in Central Park, a law enforcement official told CNN. Plus, the race to identify the UnitedHealthcare CEO shooter is hardly the first time a manhunt captivated the nation's attention. What can high-profile investigations into the Boston Marathon bombing and DC Sniper tell us about how the current search might end? CNN's Brian Todd takes a look. 

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