This person is intentionally killed, although the reason will not be known to us immediately. This is not a LOST murder mystery though, it's more of a why'd they do it. The person who dies is a crash survivor. The person who kills them will not be revealed until the November sweeps week episode (of course). The network will dangle this information for a while to build anticipation. (Another "who shot JR" moment.) The full time-line is: Death in Episode 6. Rerun the following week. Then episode 7 which is mostly told in flashback from the tail-section point of view, but ends with a teaser of who killed ________. Then Episode 8 which reveals who the killer is. Look for this person to deceive everybody except for a select few.

Here is the link to the thread on thefuselage.com: http://thefuselage.com/Threaded/showthread.php?t=22864