Recently reunited married couple Sun and Jin drowned in a submarine as they attempted to leave the mysterious island, while Sayid perished in an explosion trying to save them and his other friends. The disaster was set up by the powerful, malevolent entity inhabiting John Locke's body, then actually triggered by a well-meaning Sawyer.
The three characters who died appeared on the show from its first season. Their demises occurred as the series is wrapping up its sixth and final season.
However, even though they are dead, the characters could return in the show's flash-sideways alternate reality since they are still alive there.
Asked why the creative team of "Lost" decided to kill off the beloved characters, producer Damon Lindelof told EW.com, "Because now you know this show is willing and capable of killing anyone."
"There is no ambiguity," added producer Carlton Cuse.
"There will be very little debate at the end of this episode that (Fake Locke) is evil and bad and has to be stopped," Cuse said. "The main narrative reason for him killing our main characters is to establish how much of a bad guy he is and to clearly identify him as the antagonist rolling into the end of the series."
Yunjin Kim plays Sun, Daniel Dae Kim plays Jin, Naveen Andrews plays Sayid, Terry O'Quinn plays Locke and Fake Locke, and Josh Holloway plays Sawyer.