Catherine Herridge reported on "Shepard Smith Reporting" about ISIS claiming responsibility for the attack on a Muhammad cartoon event in Garland, Texas.

Herridge said that a counter-terrorism source found during a review of social media traffic that at least one of the shooters had contact with established overseas ISIS accounts.

"In particular, there were two tweets that [their] attention was drawn to," Herridge said.

Herridge reported that the first tweet mentions that the men will be missed after the attack, giving a sense of prior contact. The second tweet even calls one of the shooters "a man of wisdom," Herridge pointed out.

A third tweet from the account of the late terrorist leader Anwar al-Awlaki also references the shooting with #texasattack.

"When you look at the social media traffic now, there's a real discussion over whether this attack was inspired by or directed by ISIS," Herridge said, adding that that is somewhat of a "false debate."

She explained that ISIS operatives and sycophants have what amounts to a "standing order" from the terror group to launch attacks at a time and place of their choosing.

"Kind of a carte blanche, if you will, to be terrorists," Herridge said, explaining there's no tweet, email or text specifically instructing, "Now is the time."

Watch the full report from "Shepard Smith Reporting" above.

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