Bell-Jeff dropped to 3-5 overall and 0-2 in league, while St. Anthony improved to 3-4, 1-1.
Ahead, 13-6, at the break, the Saints scored on their first two drives and a punt return.
St. Anthony's Javen Lopez, a 6-foot-3, 180-pound junior running back, scored on a 20-yard run. Senior quarterback Donny Torres jumped over a crowd of linemen for a one-yard score. And then Lopez scored again on the return to help the Saints take a 33-6 lead with 2:43 left in the third.
"That was the game," Aguirre said.
"I guess we just weren't ready on defense," said Bell-Jeff running back Josh Martinez. "We came in here, I hate to say it, a little cocky. They're a good team and they played a good game. But we didn't bring 100% tonight."
Martinez helped carry the load for the Guards. He had 24 rushing yards on eight carries, including a one-yard scoring run with 1:03 left in the first quarter to tie the game at 6.
But Bell-Jeff had no answer for Lopez, who scored four touchdowns and finished with 193 rushing yards on 25 carries.
The Guards had only 21 rushing yards at halftime and finished the game the game with 33.
Quarterback Mitch Kellogg completed five of 18 passes for 89 yards, including two second-half interceptions with the game out of reach.
It was the fourth loss in five games for the Guards, who have two league games remaining at home.