Kyle has a mission to hunt down the man known as 'The Butcher'. They lay a trap for him, but their convoy is soon under attack, and Mustafa the enemy sniper pins down Kyle so he is unable to help a local man who was going to deliver the Butcher to the Americans.
Later, they manage to track his next location and break into a nearby apartment to keep watch. The homeowner is welcoming, but Kyle notices bruising and wear on his elbows that can only come from crawling on rough terrain, like a sniper - and Kyle finds a weapon stash under some floorboards. They make the homeowner enter the hideout, where he tries to double-cross them so Kyle, up in a sniper position, takes him out.
The Butcher and several of his men manage to escape, but Kyle chases after their vehicle and guns them down.
A little later, on another mission, Biggles (a friend of Kyle's) is shot in the face by Mustafa. He is flown home for surgery, and Kyle returns with his friend. Back home, although he is a hero to men who know him, his wife cannot understand his need to return to Iraq and stay away from their children. Chris feels compelled to return as he knows he is good at his job, and worries about the lives that will be lost if he is not in the field.
Soon enough he returns for a fourth tour. At one point he takes out another insurgent with an RPG - but a young boy proceeds to pick it up. Kyle is almost in tears at the prospect of shooting him, and thankfully the boy drops the weapon and runs away. He also hears from a member of his team that Biggles didn't make it through surgery.
Later, while on a rooftop in enemy territory, somehow he can sense Mustafa, the enemy sniper, a mile away in the distance. Knowing that if he shoots his gives away their position, he disobeys his commander and takes the shot - killing his enemy. All insurgents in the area flock to the source of the gunshot and surround the building. Help is too far away. Kyle phones his wife and tells her he is ready to come home now. A sandstorm blows into the area just in time as their ammo is low, and they manage to make a getaway, although Kyle has been shot.
Back in America, he is suffering from post-traumatic stress, but an enlightened doctor helps Kyle help himself by looking after other veterans. He makes amends with his family and leads a good life - until one day he takes a troubled vet out on a shooting trip - and is killed by the man.
His funeral service is held at the Cowboys Stadium, and thousands line the streets to honor the life of the man who saved hundreds of lives, and held the record of 160 enemy kills for a sniper.