Johnson's second field goal less than a minute later was the dagger.
Johnson scored 15 of Arizona's final 16 points and the Wildcats advanced to the West Region Final following a 70-64 triumph over San Diego State on Thursday night.
The Pac-12 Player of the Year Johnson began 0-of-10 from the floor before his layup gave Arizona 56-51 lead with 2:46 left. After J.J. O'Brien made two foul shots, Johnson knocked down a right wing triple to extend the margin to 59-53 with 1:52 on the clock.
Johnson hit all 10 of his foul shots down the stretch to send top-seeded Arizona to its first Elite Eight since 2011.