Kean's history is largely unknown. He was however, stationed in the South China Sea with his squad of Marines on pirate deterrence for six months prior to the events of Countdown to War.
Kean and his squad were sent on a covert mission led by CIA agent Kovic to the Korean-Chinese border to extract Highbeam, a North Korean defector who had been the lead programmer of the country's nuclear program.
After arriving at the meeting point, Kovic orders Kean and the others to surround Highbeam's vehicle in case something happens. Kovic then approaches Highbeam, telling him that he can exit the vehicle and is safe. Highbean suddenly makes a run for it, only to be stopped and nearly restrained by Kean. Highbeam then shouts, yelling for them to get away from him.
It is revealed that Highbeam has explosives strapped to his chest, and before Kean has time to react, the bomb detonates. Highbeam is killed instantaneously while Deacon and Kean are critically wounded. The explosive launches Kean fifteen feet away, blasting his arm off. Kean then reaches his remaining arm toward Deacon who had dragged himself to him first, only for Kean to succumb to his wounds.