Sexton was born in 1970 in Cupertino, California, the older of two children to Patricia K. Bolen and Thomas H. Sexton, both of whom were X-ray technicians for Kaiser Hospital. He attended Lincoln High School but did not graduate. In 1995, he started in the game industry at Condor Inc. as an artist and animator, working on NFL Quarterback Club II for the Game Boy and Game Gear. In late 1996 Condor was purchased by Davidson & Associates, and changed its name to Blizzard North. He was an artist and animator on Diablo, animating all of the heroes and many of the monsters, creating many of the story-based quests, and co-creating the "Random Item System." He also did art, animation, and design for Diablo II, modeling and animating many of the characters, as well as designing quests, and character and monster skills. He was lead designer for the game's "Random Name System" which included both items and monsters.
Sexton married in 1990, but divorced in 2002. In 2005, he left Blizzard North to co-found Hyboreal Games with other Diablo veterans Michio Okamura and Steven Woo, where he was Vice-President. Hyboreal became U.I. Pacific in late 2006, where Sexton, as of 2007, is Design Director.