Continuity mistake: Katniss, Coin and Heavensbee are discussing Katniss staying in 13 and shooting some propo's to show she is still alive. Heavensbee has a pen in his hand that has the cap off. Camera cuts to Katniss and then back to Heavensbee and the pen lid is now replaced. In the shot of Katniss we see his arms and they do not make the motions of replacing the cap. (00:23:30)





Answer: Coin was ultimately responsible. Coin sent Prim to the Capitol and then had the Capitol bombed. The rebels, led by Coin, used hovercrafts with the Capitol insignia on it to drop the bombs so that the public thought it was the Capitol bombing their children. Coin wanted Katniss to blame Snow for Prim's death to get her full support.
Bishop73