The Train- Tale With A Twist

They boarded Washington bound Amtrak train at Penn Station.  They found seat number seven and relaxed.  They were on their honeymoon.  They were oblivious to all.  Seated in four was a knockout marine sporting crescent tattoo on nape of his neck. 
The lovebirds were posing in front of Lincoln Memorial.  Marine offered to take their picture.   They cuddled on the stairs, he snapped and left.  
Bomb Squad found their corpses within the hour.  They had explosives taped to their bodies.  They were Mr.  & Mrs. Ali Abdullah from Yemen.
The Marine peeled crescent off his neck, messaged “Seventy Eight and counting”, fondled Star of David on inner arm and smiled.