During the Lightmass Offensive, Gyules and the rest of Alpha Squad were assigned to escort the resonator into the Hollow. However, contact between Alpha and the CIC was lost, so Delta Squad was sent to find them. Gyules and his entire team (with the exception of Rojas and two other unidentified Gears) linked up with Delta Squad outside of the Tomb of the Unknowns. He survived the Locust ambush that saw the death of Lieutenant Minh Young Kim and another Gear in Alpha Squad, and retreated with the rest of the surviving Gears into the Tomb. Once inside the tomb, he assisted Augustus Cole, Dominic Santiago and Damon Baird in barricading the door with large bricks while Marcus Fenix contacted Control to inform them of Kim's death. When he heard a Berserker approaching, Gyules panicked and ran away. Ironically, he was trying to run away from the Berserker, but instead went straight to her around the corner from Delta Squad's position. He was brutally ripped to shreds as his squadmates stood frozen in horror around the corner, listening to his screams and seeing his head be thrown at a wall. Marcus Fenix later found his COG Tags and collected them to be sent to his family.
Gyules' name is said once in-game silently by Baird, right before the Berserker crashes through the wall. It is also mentioned in the credits as "Redshirt Gyules", a reference to Star Trek, where the characters wearing red shirts are characters who have little to no personality and almost always die.
All the generic characters like: Anthony Carmine, Jan Rojas and Gyules in the original Gears of War game were all given names that related to the color red to reference the fact that they were red shirts.
"Gules" is the term used in heraldry to refer to the color red.
An unnoticed error regarding Gyules in the original Gears of War is that his character model doesn't wear a consistent COG Combat Helmet during his appearances. He wears the first variation while he is outside the tomb and the third variation when he is inside the tomb.
In Gears of War: Ultimate Edition, Gyules wears the first variation of the helmet almost throughout his entire appearance. Except when the Berserker kills him, it throws the third variation helmet at a wall.
Gyules final line was changed in Gears of War: Ultimate Edition, in the original Gears of War his final words were: "Oh, man, we're fucked... we're fucked! I'm getting outta here! ...'OH, SHIT!!!"