I dubbed the scene "Shadows on the Wall" The shadows are the people who were next to this "suicide bomber" on one fateful day. The blast heat was so intense, that it turned everyone around it to ash, leaving their imprit stained on the wall. 

There was a number of people who died, but it was one off. The shadow of the bomber was not seen. People say that the shadows are of the people who died and went to heaven. The bomber never went to heaven...
But later in the movie, it is told that it wasnt a bomb that killed them, but an explosion inside of a military solider. This solider had a substance called "Extremis." Extremis is supposed to be a cure for soliders who have lost limbs, as it can regrow them. 
But Extremis reacts differently with people, as sometimes the body accepts it. But sometimes it doesnt, and the outcome is the "bombings."

"That's mainly because the attacks themselves aren't treated cartoonishly. While we don't see corpses—everybody just gets vaporized—we're acutely conscious of death and destruction. In one of the movie's eeriest images, when Tony travels to Tennessee to glean clues at the site of an earlier bombing, the victims' shadows have been preserved on a wall by the blast, surrounded by the all too familiar decor of a homemade memorial: candles, cards, and so on."