There is a similarity between JFK and the Boston marathon bombing. In both instances the perceived culprits didn't take flight. Oswald hopped on a bus, got off then walked around, and went to a movie theater. The Boston guys didn't try to leave town. I'm guessing both parties had handlers they were supposed to meet and things didn't go the way they planned. Oswald easily could have been on his way to Mexico and Canada is about 5 hours drive from Boston.