Tchen was one of the mercenaries that worked for McKenas Cole, who's sole purpose was to destroy the SD-6 HQ and retrieve a box from the security vault.
Tchen only served as a minor mercenary and only checked the areas around SD-6 for intruders. Tchen encountered Sydney and was knocked unconscious by her. She demanded that he tell her where Cole was, but Tchen denied her request, so she knocked him out again and hid his body in the closet.
When one of Tchen's friends, Endo, tried looking for the intruder, he thought he/she was in a closet. Endo recklessly fired at the closet, only to realize that he just killed Tchen. He then comically said after Cole asked what happened to Tchen that he killed him.