I don't get this...(SPOILER- if anda haven't read Mockingjay yet)

After all, whose bombs were? The Capitol's?? Could be, they did put the kids there, and not for their protection. But still, what Snow berkata seemed true... And yeah, Gale designed the whole thing- I thought it was horrible before I knew they will kill a bunch of children, including Prim. But why on earth did they send THEIR OWN medics to help the others? I'm quite dizzy. Do anda think Prim just jumped to help the kids- she is that kind of person...- although she knew about the bombs?? Still, she wasn't the only one to do this but... Could Coin send them all, just to kill Prim and destroy Katniss?