"The federal government has viewed for years that he has this almost mystical ability to fabricate weapons or bombs almost out of thin air, " Kleinman said.

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They were sweeping the area, maybe they were checking for bombs or weapons, perhaps in advance of the opening ceremony.

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The agency's undercover agents recently tested current private screeners at airports around the country to see how many fake weapons, guns and bombs it would get past the screeners.

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U.S. officials have decided that cyber-weapons are akin to nuclear bombs, so destructive that only the American president can let them loose.

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But only 8% of these bombs were guided weapons.

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Investigators have been asking Tsarnaev whether there are more bombs, explosives caches or weapons beyond those already found by police, and if anyone else was involved in the attacks, a source with direct knowledge of the investigation told CNN.

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Investigators have been asking Tsarnaev whether there are more bombs, explosives caches or weapons beyond those already found by police, and if anyone else was involved in the attacks, a source with first-hand knowledge of the investigation told CNN.

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Combat units report finding several weapons and explosives caches, along with car bombs and other homemade explosives.

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As with nuclear bombs, the existence of cyber-weapons does not in itself mean they are about to be used.

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