Willits is a computer science and business graduate of the University of Minnesota and a former member of the University of Minnesota Army ROTC program. Willits was the battalion cadet-command sergeant major (C/CSM) during his junior year and attended ROTC Advanced Camp at Fort Lewis, Washington during the summer between his junior and senior years of college. After an injury during the summer, Willits completed two rotations, being assigned to both the first and seventh cadet regiments during that summer. He held the rank of cadet-major (C/MAJ) during his senior year and was assigned as the battalion training officer.
Willits has stated in numerous interviews that he was inspired to make video games when he downloaded a demo version of DOOM in 1992. Playing the first room of Level 1, he thought that was the entire demo until he discovered a door that leads the player to the other rooms. It was that moment when the door opened, Willits knew that he wanted to pursue a video game career. He joined id Software in 1995 after impressing the owners and development team with Doom levels he forged in his spare time and distributed free over the Internet. Willits has worked on Strife, The Ultimate Doom, Quake, Quake II, Quake III Arena, Quake III: Team Arena and Doom 3.