Gale didn't kill Prim. It was actually that Coin lady. Which at first I thought it was Snow.
After the reaping before she leaves District 12, she is visited by Madge who gives her the mockingjay pin, Gale, Prim and her mom, and the Baker who gives her cookies.
Katniss doesn't kill Prim, Coin does. She does because she was afraid Katniss might want to stand up and be president.
Prim dies on page 406
The locket that Peeta gave Katniss in Catching Fire is gold and has a mockingjay ingraved in the front, inside the locket there is a picture of Gale and her mother and her sister Prim.
*SPOILER ALERT* He does not kill her directly. He is the one who created the bomb design of the bomb that killed her. Katniss dislikes him now for this.
Technically, President Coin kills Prim, since she sends the order to send down the parachutes that explode, ultimately killing Prim.But, Gale and Beetee play a part in Prim's demise, too, without even meaning to, as they created the bombs that killed Prim.
It was President Coin. She used the bomb design from Gale, who didn't know that it would kill Prim. Katniss reckons that Coin deliberately put Prim in danger - deliberately killed her - to win Katniss's favor. So, Gale designed the bombs, but Coin set them off.
Gale doesn't kill prim. His bomb design does. He designed bombs that blow up, people go to help the others, then his bombs explode a second time. Plutarch and Coin release the bombs into the group of children, then when prim goes to give medical attention to the children, The other bombs go off and prim dies.
When Katniss is taken into the justice building, she gets three sets of visitors. The first is her mother and Prim, the second is Gale, and the third is Madge, the mayor's daughter. She gives Katniss the mockingjay pin that becomes a major part of the trilogy.
After the reaping before she leaves District 12, she is visited by Madge who gives her the mockingjay pin, Gale, Prim and her mom, and the Baker who gives her cookies.
Katniss doesn't kill Prim, Coin does. She does because she was afraid Katniss might want to stand up and be president.
Gale comes to visit Katniss in the hospital after she gets hurt from flying shrapnel. Gale and President Coin blew up the courtyard of children in which Prim was helping the injured, Prim (Katniss' Sister) was killed in the explosion. When Gale comes to visit he asks her if shell ever be able to forgive him, she doesn't answer because she is so mentally hurt at this time. After that Gale takes up a government place in District 2 and we don't hear from him again. Hope this helped :)
Prim dies on page 406
By hunting with Katniss, Gale helps to provide food for Katniss' mother and Prim.
No
Gale Hawthorne kills Prim
*******SPOILER ALERT****** finnick dies, prim dies, capitol falls, katniss kills the president from district 13, because she had something to do with prim's death, gale leaves district 12, katniss stays with peeta and has two children.