"Isaac [Chance] gave me a really good ball, and I just hit it," Alexander said. "I practice it all the time, and it was a real good opportunity. I loved it."
The Mustangs (14-1-3) reach the final four for the first time in school history and will face Bingham in Tuesday's semifinals at Woods Cross High.
In a physical game full of hits and tackles, the hardest hit just might have been levied by Herriman coach Ryan Mitchell, who lifted Alexander then tackled him to the turf in the postgame celebration.
Each team scored on a set play in the first half. Herriman's Carter Johnson scored on a free kick from just outside the top of the goal box in the third minute. Viewmont's Drake Cook answered in the 21st minute when he converted a penalty kick awarded after teammate Sean Cella was tackled in the box.
It was a game of possession and patience from there as both teams were turned away on the few runs they could muster. Herriman's patience paid off in overtime.
"A bunch of us have played at a high enough level that we've gone far in tournaments," Herriman junior goalkeeper JD Myers said. "But to go this far in state, when at the beginning of the season everyone's saying, 'Herriman's not going to be this, and not this,' we came out and played our game and we show everyone that we play together as a family.
"Going to the semis as a family is the best thing you could ask for."
Viewmont, which had outscored opponents 24-2 in its previous eight games, ended the season 12-3-1.
Herriman 2, Viewmont 1 (OT)
• Ethan Alexander's goal three minutes into overtime sends the Mustangs to the state semis for the first time in school history.
• Drake Cook scores on a penalty kick in the 21st minute for defending champion Viewmont.
• Carter Johnson scores his team-leading 13th goal of the season three minutes into regulation on a free kick.
Class 5A state tournament
Friday's quarterfinal scores
Copper Hills 1, Weber 0
Layton 4, American Fork 1
Herriman 2, Viewmont 1
Bingham 2, Fremont 0
Tuesday's state semifinals
at Woods Cross High
4:15 p.m. • Copper Hills vs. Layton
6:30 p.m. • Herriman vs. Bingham