California student catches alleged thief on camera: a teacher - KiiiTV3.com South Texas, Corpus Christi, Coastal Bend

Courtesy ABC News

A California high school student was shocked at what she found when she decided to play detective and stop a string of thefts from backpacks during gym class.

Justine Betti said she decided to hide in a locker to see if she could catch the thief in action. She didn't expect the alleged culprit to be her gym teacher.

After all of the students left the locker room, the teacher stayed behind, rummaged through backpacks and took money, Betti said.

"Something needed to be done. That's not okay," she told ABC News' Sacramento affiliate KXTV.  Betti is a sophomore at Linden High School in Linden, Calif., about 60 miles southeast of Sacramento.

Betti decided to hide in the locker again — this time, with a cellphone camera to record what she saw. She set up a second camera in another locker to get two angles.

Once again, she said she saw the teacher go through the bags.  Her video shows someone digging through the bags, and one video appears to show the person taking something out of a pink duffel bag.

"I didn't want to believe that she would do something like that because she was so nice, but then she did it," Betti said. "It was really scary. I was like, ‘Oh my gosh. I can't believe I just got this on video.'"

Betti said she kept watching it "over and over" and eventually took the video to her principal with some friends.

"He said that he'll investigate it and he told us to delete the video, but I had already sent it to my dad," she said.

The teacher is on administrative leave, according to KXTV. The Linden School District told ABCNews.com that it is investigating the matter, but the superintendent did not immediately respond to requests for further information.

The teacher has not been identified, but is a 30-year teaching veteran described as a "great teacher" by many students.

Betti said she struggled with recording and sharing the video, but said classmates have supported her.

"They've been supportive and said that we did the right thing," she said. "We feel like we did the right thing, but it's still kind of hard."