Players first meet Gaz at the very beginning of Call of Duty 4. He is the instructor during the firearms exercise at the start of the game. It is also mentioned that he has the fastest time in running the practice course that is set up to resemble the cargo ship on which the game's introductory mission takes place. The dialogue shared between him and Captain Price sets the tone for the missions and displays the close relationship that the two have. Gaz is voiced by an English actor called Craig Fairbrass, who was fairly popular in the 90's.
Gaz is with the player throughout the campaign in all of the S.A.S. missions. Although he is an important character, he never appears to be much more than an AI squad mate, as the game still leaves the crucial duties up to the player. He sometimes splits off from the player during missions, supposedly taking a separate path and completing a separate objective. This becomes the case in the later joint operations with the United States Marine Force Recon, when trying to stop the nuclear ICBM launch initiated by Imran Zakhaev in response to his son's suicide. During the second to last mission, in which the task is to locate the missiles' launch control center, Gaz takes a separate path through the facility, to find the main security room, open the emergency doors, and give "Soap" and Cpt. Price access to the control room. After that objective has been completed and the nuclear launch aborted, Gaz drives the truck in which the squad escapes the launch facility, pursued by Zakhaev's forces. When the chase is over, Gaz remains fighting the Ultranationalists on the bridge. However, it is seen that after the tanker explodes, he has either been wounded by the blast or shot, and is in a condition of extreme agony when Imran Zakhaev enters the scene. Gaz is left writhing on the ground as the player watches Zakhaev kill him point blank with a pistol.
Relation to Ghost
After the release of Modern Warfare 2, there has been much speculation over the character Simon "Ghost" Riley, a Task Force 141 operative. Many have questioned whether Ghost is in fact, Gaz. Ghost and Gaz are voiced by the same voice actor, Craig Fairbrass. Riley's face is never revealed as he always wears a skull balacava and sunglasses throughout Modern Warfare 2's campaign. Riley is also executed by a shot to the head, however, so if he is secretly Gaz, his luck hasn't changed much.
"Aw, is he taking the piss!?"
"Your fruit killing skills are remarkable."