Kendra Gill, 18, of Riverton said the incident was "a silly mistake" and she would step down because there was no other option, saying she believed she would be stripped of her Miss Riverton title anyway, the Salt Lake City Deseret News reported Tuesday.
"I do believe this whole thing is a way to help us grow and to learn from our mistakes and to move forward and just kind of get on with our lives," Gill said.
Gill was arrested Aug. 2 along with Bryce Christopher Stone of Riverton, John Patrick Reagh of Draper, and Shanna Marie Smith of Bluffdale, all 18 and recent high school graduates, and formally charged Friday with four counts of the second-degree felonies of possession of an explosive device. They are accused of tossing 8-ounce plastic bottles with aluminum foil and toilet bowl cleaner from the car to experience the explosions.
Gill lawyer Wally Bugden said his client and her friends were playing a high school prank and there was no malicious intent.
No one injuries were reported.
The Salt Lake Tribune, however, said investigators said the four targeted friends as a prank.
Gill said giving up her title was one of the hardest decisions she's ever made.
"It was pretty difficult because I have worked so hard for it. But I know there are other girls out there that can do equally as good of a job, and I'm not worried about that at all," she said.