The battle at the helicopter was the climax of the tension between the Others (with help from Sayid and Kate) and the Kahana mercenary team. This battle was the final defeat of the mercenary team: Kocol, Lacour, Redfern, and Omar were killed in the attack by several Others, while Keamy was badly wounded and was killed shortly afterward by Ben at the Orchid.
Having successfully captured Linus, Martin Keamy, the mercenary team's leader, and his men returned to the helicopter; however, prior to his capture, Linus had signaled some of his people who waited at the helicopter to ambush the mercenaries. ("There's No Place Like Home, Part 1")
Keamy prepares for the attack.
Kate was sent unarmed to infiltrate the mercenary team and remain with Benjamin Linus during the attack. Running up to the mercenaries, panting and out of breath, Kate claimed she was being chased by "his people", motioning towards Ben. Keamy sent Lacour and Kocol to scout the nearby woods, while Redfern guarded their flank.
The Others' assault used a combination of primitive, conventional, and high-tech weapons and methods: an Other killed Kocol by jumping out of a tree and snapping his neck; a second Other Lacour by snaring his legs and tripping him, presumably killing him off-screen by an unknown method; a third Other lethally electrocuted Redfern with a stun dart.
Gunfire was then exchanged between both sides, and sensing an opportunity to flee, Kate led Ben out of the fray and into the jungle. As soon as Ben was away, an Other threw a grenade at the helicopter. The helicopter's pilot, Frank Lapidus, who was handcuffed inside, shouted a warning and Keamy kicked the grenade away, accidentally killing his last subordinate Omar.
Keamy pursued Kate and Ben into the jungle, where he was ambushed by Sayid and the two engaged in hand-to-hand combat. Keamy overcame Sayid, but Richard Alpert came from behind, shooting Keamy in the back.
Richard Alpert shoots Keamy.
The mercenaries were all killed after the attack, except for Keamy, who was saved by an armored flak jacket and his ability to feign death for an extended period of time. Later, Keamy proceeded to the Orchid and traveled down the elevator to the station. After stating that Richard was "Ben's boyfriend" and a coward who shot him (Keamy) in the back, he taunted Ben enough to eventually be killed by him in a fit of rage for killing his daughter. This set off the dead man's trigger, which destroyed the Kahana, killing Michael, the rest of the crew and at least 10 survivors who had already travelled to the safety of the freighter. ("There's No Place Like Home, Part 3")