In Mockingjay, Katniss defied Gale's wishes when he was captured because she didn't want to see him dead. It seems like a nice thing for her to do, especially since Gale is soon able to escape out of the Peacekeepers' grasp because of the rebellion's "distraction".
He ends up working for government in district two. The book doesn't mention what he is doing but the movie says he was promoted to a Military Captain. Either way Katniss believes he will forget about her and move on with his life. While Katniss cared about Gale, it was Peeta she couldn't live without.
In the end, Katniss and Gale grew apart, as many childhood friends and young loves do. She needed something different in her life, and with Gale's link to Primrose's death, Katniss found a reason to cut ties. If Katniss ever wanted to find comfort again, she knew she had to return to Peeta for the long term.
Prim was among the medics who arrived to treat the victims. Unfortunately, a second batch of bombs were set off, with Prim being killed in the explosions. Gale was not the one to drop the bombs from the hovercraft, but he was one of the key figures to devise the strategy of double bombings.
Katniss comes close to crying, something she knows she mustn't do because it would indicate weakness to the other tributes and make her look vulnerable; thankfully, Haymitch distracts the crowd and the cameras by stumbling off stage.
Hunger Games: Why Katniss Ends Up With Peeta, Not Gale
Who killed Prim Hunger?
Before the Capitol battle, Gale had explained to Katniss his series of bombs designed to feed off human compassion: a small bomb would go off, and then when medical aid rushed in, a second bomb would go off, killing those people as well. Incidentally, it's this exact type of bomb that took Prim's life.
Answer and Explanation: Prim is killed by a bomb at the very end of the battle. Alma Coin sees an opportunity to turn the Capitol troops against Snow, and she decides the resulting loss of life from her plan is a worthwhile price to pay.
The double bomb that kills Katniss Everdeen's sister, Primrose, was designed by two rebels: Beetee and Gale, Katniss's lifelong friend. Previously, Gale had explained that the double bombs are designed to appeal to mankind's weakness for compassion.
Prim's death was necessary for Katniss to see the true evil of Coin. This also allowed Katniss to hate Coin on a higher level and have a motive to kill her. Finnick's death was also necessary because he protected Katniss and the others of the Star Squad during the lizard mutt attack.
Conclusion: Yes, Gale was indirectly involved with Prim's death, as in if he didn't create the bomb then she wouldn't have died. But what if someone else invented it? Gale did not kill Prim.
Although she will never know for sure, Katniss does recognize that she cannot be with Gale. She will never be able to forgive him for his idea — the parachute bombs — that killed Prim.
In Catching Fire, people who have never met or barely know them think that Gale is her cousin. Gale admits to have fallen in love with Katniss in Catching Fire.
Gale does not marry anyone in The Hunger Games. He and Katniss talk about running away together and starting a new life in the wilderness, but they never officially marry.
Who does Gale end up with at the end of Mockingjay?
In the Mockingjay movie, Katniss confronts Gale about his role in Prim's death, which he struggles to come to terms with. Katniss, unable to look at him the same way, lets him walk away without a word and eventually ended up living with Peeta.
At the end of Mockingjay, Gale relocates to District 2 and begins working in the district's government. He helps train replacements for the Capitol's Peacekeepers.
Finnick's death gave even more weight to Katniss's mission to kill Snow, since he was directly responsible for the death of one of her friends - making it all the more poignant when she chooses to kill President Coin (Julianne Moore) instead of getting to personally kill Snow herself.
Cressida is a talented director with a keen eye for useful footage. Her desire to film Katniss in action is so great that she lies about Katniss's plan to kill Coriolanus Snow in the hopes that Katniss will act heroically on camera.
What would have happened if Prim went to the Hunger Games?
If Katniss hadn't volunteered, Prim most likely would have been killed and would not have won as her sister did. Prim was an intelligent, compassionate, and courageous individual with excellent medical skills, but she didn't have the combat skills or selective ruthlessness needed to win.
In the end, Katniss and Gale grew apart, as many childhood friends and young loves do. She needed something different in her life, and with Gale's link to Primrose's death, Katniss found a reason to cut ties. If Katniss ever wanted to find comfort again, she knew she had to return to Peeta for the long term.
According to the star behind Effie, Elizabeth Banks, she and Haymitch's Woody Harrelson improvised the scene. Considering she's been adamant about the characters having some romantic connection, it only makes sense that they'd share a goodbye kiss. It's very on-brand for Effie, as well.
Alma Coin was the true villain of The Hunger Games, with Katniss actually seeing her as more of a threat than Coriolanus Snow. At the same time, it was Snow who was made out to be the bad guy in previous movies, making some question why Katniss killed Coin and spared him.
