The discovery was made after officers from the Richmond County Board of Education seized the Hephzibah High School teen's phone Monday as part of a separate investigation, according to Richmond County Sheriff's Lt. Calvin Chew.
On the phone, they discovered a short video showing the child playing with a stuffed animal, Chew said. Both the mother and the teen can be heard encouraging the child to simulate sexual acts.
"At one point the guy comes in and says: 'Why you doing the bear like that, it's nasty,' " Chew said. "But he's laughing and keeps taking the video."
In another part, the mother asks her son why the toy bear appears to be performing a sexual act on him. The child responds by pushing the bear's face to his private area, Chew said.
"You can hear the mother in the background laughing and making comments about it," he said.
Investigators have charged both the teen and the mother with felony sexual exploitation of a minor.