"My first reaction was to sit down and hide. Then I heard an American say 'go get him'."

From Ace of Spades HQ:

That was once typical of Americans, and, who knows, maybe will be one day once more.

Jazz Shaw digests the more vetted version of the story -- none of the US personnel on the train were Marines. The three who first acted were an Air Force man, a National Guardsman, and a civilian.
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He says the most important hero here was Spencer Stone, the Air Force man, who was actually a medic. Stone got badly slashed by the terrorists' knife or boxcutter, and his thumb was nearly cut off entirely. (Hopefully that has been reattached and will heal with no complications.)

Despite bleeding profusely, and despite being down a thumb, Stone administered emergency aid to a passenger badly slashed through the throat immediately after subduing and hogtying the terrorist. Hopefully that passenger will live, and Stone will have another contact/informant in his Shadow-like war on crime.
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AMERICA

Our medics will kick your "Holy Warriors'" asses up and down the block