A high-scoring first quarter ended with Buena Vista holding a touchdown lead, 14-21, heading to the second quarter.
Each team scored in the second quarter leaving the Bruins trailing by seven, 28-21 at halftime.
The Bruins failed to score in the third frame with the Demons tacking on seven points to make the difference 35-21 with one period left to play.
Each team scored six points over the final eight minutes of play for a final score of 41-27.
Junior Dusty Emig rushed for 48 yards and two touchdowns for the Bruins with Wade Barnard collecting 100 yards and a touchdown and senior Jared Reynolds carrying the ball 16 times for 98 yards and a score.
Buena Vista's Parker Johnson crossed the goal four times with 172 yards rushing on 15 carries and teammate Drew Martin toting the pigskin nine times for 178 yards and two touchdowns.
The Bruins finished with 350 yards of offense and Buena Vista racked up 384 yards.
The Bruins (1-1, 1A WSL) are in Aspen (1-1, 2A WSL) this Friday with kickoff at 7 p.m.