A veteran police officer with one of the nation's most prominent transit systems has been arrested for allegedly trying to help ISIS, ABC News has learned exclusively. Authorities believe that while working for the Metro Transit Police Department around Washington, D.C. – a community he swore to protect – the officer was also trying to assist ISIS operatives find more ways to communicate in secret, sources told ABC News. The officer allegedly purchased technology-related items to send to the ISIS operatives so they could evade authorities when contacting each other, according to the sources. Instead of allegedly engaging with true...