Landale, who finished with 10 points, put Saint Mary's back on top 66-65 with a pair of free throws with 1:41 left. Emmett Naar then hit two more from the line with 13 seconds left to cap the 12-2 run and Pacific's Alec Kobre missed a 3-pointer just ahead of the buzzer.
Joe Rahon had 13 points, including a key pair of 3-pointers late in the game, for the Gaels (18-2, 9-1 West Coast Conference), who forced 14 turnovers.
Trailing most of the night, Pacific (6-14, 4-6) clawed back with a 15-2 rally that included three straight 3s from Kobre, making it 61-54 with 4:48 left.
Kobre finished with 18 points to lead four Tigers in double figures.