DAVE MARQUIS, KXTV[/*][/list]LINDEN, Calif. (CNN/KXTV) - A California student sets up a hidden video camera hoping to catch a thief and ends up busting a popular teacher."I was really scared. I was like, 'Oh my gosh. I can't believe I just got this on video,'" said student Justine Betti.It began when students in Betti's gym began noticing money and other items missing from their backpacks. She decided to hide inside a locker to watch, never imagining what she would see."I didn't want to believe that she would do something like that because she was so nice, but then she did it," said Betti.Her very popular teacher and 30-year veteran was going through student backpacks, appearing to take money."Something needed to be done. Like, that's not OK," said Betti.Betti said she felt she had to do something and put herself in a locker again -- this time holding a phone video camera, putting another phone camera in another locker."Right when I got the video, I was like, 'Oh, my gosh. I can't believe I got this on video.' And I couldn't believe that I got it, and I kept watching it over and over," said Betti.She and the other girls took the video to the principal."He said that he'll investigate it, and he told us to delete the video. But I had already sent it to my dad," said Betti.Others had also sent the video out by then. It was not an easy decision to take it or share it, they say, but other students agree with the decision."They've been supportive and said we did the right thing," said Betti."Makes you feel like your privacy was invaded, but you know, you can't help but feel bad for her [the teacher], either," said student Kellie Martinez. "She was a great teacher.""We feel like we did the right thing, but it's still kind of hard," said Betti.The school district and local authorities are investigating. Meanwhile, the teacher has been placed on administrative leave.