Gale was responsible for creating weapons that would trigger a second wave of bombs to target first responders and combat healers. This invention potentially ended up killing Prim, but even if he wasn't directly responsible, Katniss found this tactic so abhorrent that she lost her affection for him.
Gale had been manipulated and used by Coin's military just like Katniss had, but he didn't mind. He believed that these evils needed to be done for the greater good, and though he regretted Prim's death, the strategy had freed Panem.
In the beginning, Katniss did love Gale. But around the middleish/ending of the story, she finds herself loving Peeta instead. The main reason, though: Gale and Coin were designing a bomb, and Prim was killed by the bomb. After she died, Gale realized it was over with KAtniss.
On the other hand, while Gale also wants to create a better world, he tends to be more violent. Gale is resentful and believes the ends justify the means. While Gale's strength was necessary to win the war against the Capitol, Peeta's peaceful personality is ultimately what Katniss needed in a person.
Gale usually sold his hunting finds to the Head Peacekeeper, Cray. But today Cray wasn't there, so Gale got caught with contraband by the new Head Peacekeeper, who punished him.
Hunger Games: Why Katniss Ends Up With Peeta, Not Gale
Why did Katniss not shoot Gale when he was captured?
Katniss refuses to kill Gale
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".
The problem was that Gale was the one who created the firebomb devices. Despite not being fully responsible, Katniss couldn't overlook his possible involvement. Katniss returned to District 12, where she reunited with Peeta after she couldn't allow herself to fully forgive her childhood best friend.
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.
He loved her even though he knew she loved Peeta. The strength of Gale's feelings toward Katniss was put to the ultimate test when he realized that she loved Peeta, but that didn't stop him from adoring her. He even volunteered to rescue Peeta because he wanted Katniss to be happy.
Gale is jealous of Peeta and the relationship he has with Katniss, and he wants Katniss to decide between them, though he doesn't press Katniss during her recovery in District 13. Gale is an excellent hunter and excels at setting snares and traps.
She later realizes, after a conversation with the imprisoned President Snow, that President Alma Coin sent Prim to her death (which was caused by a hovercraft by the rebels) both to sway the Capitol citizens to Coin's side by making them think Snow was bombing the children, and to swing Katniss to her side through the ...
When Katniss comes home to District 12, Gale immediately confesses his love for Katniss, and she realizes she might have feelings for him, too — but she can't explore them, because she has to continue her fake relationship with Peeta or else her entire family, including “cousin Gale,” will be killed.
Peeta, Annie, and Beetee vote no, while Johanna and Enobaria vote yes. After some thought, Katniss demands to kill Snow. Once she receives an agreement, she votes yes, for Prim. Realizing something is up (as Katniss would never do that), Haymitch votes yes, too.
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.
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.
Katniss feels betrayed, most of all by Haymitch, who used her and Peeta. Eventually she wakes to find Gale there. He's badly injured and tells her the Capitol bombed District 12 after the Games. He got Prim and Katniss's mother out in time, but the District 12 is gone.
He Didn't Save Peeta's Family But some people believe Gale may have had more malicious reasons for not helping them. However, Peeta's family wasn't great. His parents were abusive, or at least distant. It would have been interesting to see what would have happened had his family survived, but no one missed them much.
The love triangle between Katniss, Gale, and Peeta is a major part of The Hunger Games franchise. There always appeared to be a spark between Katniss and her best friend, but when Katniss is reaped, everything changes. To survive, she's forced to fake a romance with Peeta, a boy who lives in her district.
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.
Gale was responsible for creating weapons that would trigger a second wave of bombs to target first responders and combat healers. This invention potentially ended up killing Prim, but even if he wasn't directly responsible, Katniss found this tactic so abhorrent that she lost her affection for him.
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.
Katniss has a strong sense of right and wrong, but this in itself can lead her to make some somewhat questionable choices, especially as the series progresses.
Gale's jealousy towards Peeta stemmed from his feelings for Katniss and his desire to be with her. Even after Katniss became engaged to Peeta, Gale still harbored feelings for her and was unable to fully let go of his jealousy and resentment towards Peeta.
