The Aztecs lost the ball again moments later on a bad snap, and it took the Cougars just one play a 14-yard scamper by Jamaal Williams to find the end zone and take a 16-6 lead.
Until those two costly mistakes, the Aztecs had mostly dominated the game.
But Van Noy wasn't finished. He returned an interception 17 yards for a touchdown to give the Cougars a 17-point lead, sending scores of SDSU fans to the exits.
BYU seemed poised to tie it or take the lead early in the third quarter and seize some momentum when Van Noy blocked a punt, but the Cougars couldn't pick up a single yard after taking over on the SDSU 35-yard line, and they punted. Riley Stephenson pinned the Aztecs on their 1, but they drove 47 yards to get out of the hole before Brandon Ogletree stuffed Adam Muema on third-and-1.
The Cougars drove just inside the Aztecs' 35 again on their next possession, only to stall and punt again and see Stephenson pin SDSU at its 2.
The Cougars quickly got the ball back at their 50, though, and drove to the SDSU 4 before King Holder intercepted a pass that fell out of Hoffman's hands. On SDSU's first play, however, Dingwell lost the ball in the end zone and the game's momentum swung drastically.
The Cougars had a miserable first half, at least until the final two minutes.
After picking up just 70 yards in their first five possessions of the half, they took over at their own 20-yard line with 2:07 remaining in the half and drove 74 yards to the SDSU 6-yard line. However, with just five seconds left on the clock, Mendenhall opted to kick a field goal on second down.
Justin Sorensen's 24-yarder cut SDSU's lead to 6-3.
The Aztecs got on the board first when Chance Marden booted a 27-yard field goal after a 52-yard drive, set up by Muema's 34-yard reception.
The Cougars stopped SDSU's first drive when Spencer Hadley tipped a pass and Ziggy Ansah intercepted it. But the Cougars picked up just one first down on their first three possessions.
SDSU went up 6-0 early in the second quarter on another Marden field goal, this one from 23 yards out.
Riley Nelson came into the game in the second quarter, and was promptly intercepted by SDSU's Eric Pinkins on a tipped pass.
Pinkins returned the interception to the end zone, but a penalty nullified the apparent touchdown.
San Diego State picked up 193 yards in the first half, 85 of those on the ground, but had just a three-point lead to show for its dominance.