She said that minutes into the clip from a children’s video game, a man appeared on the screen — offering instructions on how to commit suicide.

“I was shocked,” Hess said, noting that since then, the scene has been spliced into several more videos from the popular Nintendo game Splatoon on YouTube and YouTube Kids, a video app for children. Hess, from Ocala, Fla., has been blogging about the altered videos and working to get them taken down amid an outcry from parents and child health experts, who say such visuals can be damaging to children.

One on YouTube shows a man pop into the frame. “Remember, kids,” he begins, holding what appears to be an imaginary blade to the inside of his arm. “Sideways for attention. Longways for results.”