Minnesota teen Monalisa Perez killed her boyfriend Pedro Ruiz III, 22, on Tuesday while filming a YouTube video where she reportedly fired a gun as he held a book to his chest to stop the bullet's path.
It went straight through.
The next day Ms Perez, pregnant with her second child, was charged with second-degree manslaughter, according to local media.
They used two cameras to upload the "dangerous" video to their YouTube account, which comprises pranks such as Ms Perez feeding her boyfriend a donut covered with baby powder instead of icing sugar.
Sheriff Jeremy Thornton of Norman County told New York Times: "I really have no idea what they were thinking".
"I just don't understand the younger generation on trying to get their 15 minutes of fame."
Mr Ruiz had been "trying to get her" to fire the gun "for a while", Ms Perez said according to court documents.
In their last video, Ms Perez says: “Can you imagine when we have 300,000 subscribers?”
Mr Perez responds, "The bigger we get, I'll be throwing parties."
The New York Times reported that the couple's videos only had a couple of hundred views on Wednesday.
By Friday, their last video had nearly 700,000 views.
