Hatter was 10 of 20 from the floor, made four 3-pointers, and had six assists and three steals for the Big Red (4-4), who is undefeated at home.
Lavon Long made a 3-pointer to give the Saints a 60-50 lead with nine minutes left. Hatter scored 19 points during a 27-17 Big Red surge, including three 3-pointers, to tie it at 77 with 53 seconds left.
The Saints then made 3 of 4 field goals, and Hatter and Darryl Smith each made a pair of free throws for an 81-77 lead with three seconds left.
Siena's Ryan Oliver made a 3-poiniter at the buzzer.