Carter is a character in Syphon Filter 2. He is an airman working at the McKenzie Airbase and is in charge of one of the doors leading into a Restricted Area of the base. An Unnamed Airman walks up to him while Lian Xing is slowly trying to make her escape, saying that he needs to get some air due to these "government guys giving him the creeps". Carter agrees, mentioning that they brought up a couple of body bags and their C.O. called in saying the whole place is locked up tight.
After the airman is buzzed through, Lian sneaks under the chest-level window (relatively simple design flaw in security) and makes her way to the back. She acquires her Combat Gear and gets in touch with Teresa Lipan, while observing Dillon Morgan and Elsa Weissenger telling Carter they're ready to leave. After they go through the door, Lian moves up behind Carter and tazes him so that she has access to the switch he's standing next to, allowing her to go further into the base.
In the next area, there is an airman who will approach the intercom to get Carter to let him in otherwise he'll be late for his post. This airman only approaches the intercom if you've passed through the door already. If he's allowed to keep talking, he'll buzz command and this will cause a parameter failed screen to pop up (due to Carter not responding or opening the door). Lian will have to taze this airman to continue with her mission.