After Paris, U.S. officials evaluating their own high priority concerns

(CNN)The FBI, Department of Homeland Security and intelligence agencies in the U.S. are scrubbing their databases and evaluating high priority targets living in the U.S. following the terrorist attacks in Paris.

"Whenever something like this happens you want to make sure you tighten things up," says a U.S. official with firsthand knowledge of the efforts.
The high priority targets include foreign fighters who U.S. officials say could have returned to the U.S. after fighting in Syria.
U.S. law enforcement and intelligence officials are also evaluating whether they should take any action against these high priority targets by contacting them directly.
    A U.S. official with firsthand knowledge says "whenever you're investigating someone you don't want to show your hand because that's how we collect intelligence" but in certain cases the source says you may decide to do an interview with them and give them a heads up they're on our radar to stop an imminent threat.
    The source says "it can be very subtle or very overt, but the intent and the effect is same: you let them know you're watching -- if they are in the midst of something."
    U.S. law enforcement and intelligence officials are awaiting more information on the subjects in Paris and the two recent terrorist attacks against the police officer Thursday and Charlie Hebdo before moving forward with anything, according to the source.