Tonight is Hollywood's biggest night, but that doesn't mean it's all smiles and pageant waves.

Law enforcement sources told TMZ there's "an extra knot" in security at this year's Academy Awards because of all the shootings that have happened recently in the U.S.

TMZ added that police gave a security company an information packet on stalkers who are known to have harassed celebs attending this year's Oscars: "The packets include pictures of the stalkers, which are distributed to security in the field."

So as you watch the stars on the red carpet, know there are many people behind the scenes watching out for the crazies — 'cause crazies love a good crowd, as we've seen far too often.

Source: TMZ