Keith Ham Yel Tun is a character in Grand Theft Auto, who works for Uncle Fu in San Andreas. When the protagonist goes to him for questioning, Tun explains that he failed Uncle Fu and wants to commit suicide. He does so, by jumping off the roof of the building he is on, falling to his death. The protagonist then collects the necessary items.
His name, if said fast, is a tongue in cheek reference to Keith Hamilton, the director of the original Grand Theft Auto.