More finishers are crossing the line later in the marathon than when the winners cross. The winners are also not normally American- if that was the target. Not to mention, having it go off later means they don't have to guess when winners will cross. The bomb followed by other bomb scenario immediatly made me think of Hunger Games, but then it sounded like the explosions were actually quite close together, so that probably isn't what was happening. A tiny bit of good news from ABC: 4:38 pm ET: “There is no sign of any radiological material involved in the explosion,” a federal source tells ABC News.