Throughout the country, local law enforcement agencies received two FBI bulletins, according to an official who has seen the reports and summarized them for The Associated Press. The first said that while July 4 festivities might make an attractive target for terrorists, authorities had no credible evidence that an attack was planned. The second explained what happened in London and advised local officials to be on the lookout for suspicious vehicles and activity.
Thank you BurbankKarl for that update.