The redshirt senior said he would be transferring for "personal reasons" two weeks ago, citing health concerns for his mother and grandmother.
"This is an hour-and-a-half from my mom," he told Schad. "It's the best fit."
Mark, who had 1,366 rushing yards, 12 touchdowns and two punt return touchdowns in 2012, played in only three games last season because of leg injuries. He was interested in FBS schools such as Baylor, Houston, Texas State, Oklahoma State, Texas Tech and Kansas, Schad reports, but he "couldn't gamble" with his last year of eligibility.
By going to an FCS school, Mark can play immediately.
Had he stayed at Northwestern, Mark would have been suspended for two games due to violation of team rules. But he said his reason for leaving stemmed from his mother's and grandmother's health issues, not the suspension.
"I will get my Northwestern degree," Mark told Schad. "There is no bad blood with Northwestern at all. Me and Coach Fitz [Pat Fitzgerald] still talk. We are still family."
Mark, who has already practiced at West Texas A&M, said his goal is to play in the NFL next season.
- Chris Mascaro