Vargas

Crewman Vargas was a member of the Starfleet battalion under the command of Captain Loomis which was sent to protect a captured Dominion Communications Array on the planet AR-558.

After 7 months of prolonged combat with constant waves of Jem'Hadar soldiers, Vargas had grown tired and developed a negative attitude that was reinforced by his grim surroundings. He was slso afflicted with several health problems, such as breathing difficulties, due to his stay there.

Vargas also went partially-insane following the sudden death of Crewman McGreevey, who, even though Vargas hated due to the fact he "never shut up", McGreevey liked him and treated his wounds until the day he was killed.

Vargas was part of the defense of the array during the Jem'Hadar's last attempt to retake the Array. Though many Jem'Hadar were killed by Houdini mines and Starfleet phaser fire, they overran the defenses and engaged the Starfleet troops in hand-to-hand combat. Vargas himself was able to kill three Jem'Hadar soldiers single-handedly by that point; his back was exposed for a split-second; enabling another Jem'Hadar trooper to jam his k'tar'kin blade in the back of Vargas's skull. He died instantly.

(DS9: The Siege of AR-558)