Denver trailed 29-21 at halftime, but rallied in the second half and Brett Olson heaved a shot from near half-court at the buzzer to tie it at 63 at the end of regulation.
Alexander made two free throws and layup and the Bison led 69-65 in overtime, but Cam Griffin dunked to pull Denver within 69-67. Cam Delaney fouled Alexander, who made both free throws, then Nate Engesser hit a layup with two seconds left and Denver trailed 71-69. Jalen Love fouled Alexander on the next Bison possession, and he made both free throws.
Olson led Denver (10-14, 4-7) with 22, Griffin had 15 and Engesser 10.