A pregnant teenage mother has allegedly shot and killed her boyfriend through a hard cover encyclopaedia book in a failed YouTube video stunt.

Monalisa Perez, 19, allegedly shot Pedro Ruiz III through a book he held at his chest using a powerful .50-caliber Desert Eagle pistol.

The Minnesota, US, couple’s three-year-old daughter watched on as Ms Perez shot the 22-year-old from about 30 centimetres away, it’s alleged.

A criminal complaint filed by the Norman County Sheriff, obtained by the Star Tribune, said Mr Ruiz had set up a camera on top of a ladder and at the back of the car to film the stunt.

He believed the book was thick enough to stop the bullet from hitting him, and had pressured Ms Perez to carry out the stunt with him, she alleged.

Hours earlier, Ms Perez posted on Twitter: “Me and Pedro are probably going to shoot one of the most dangerous videos ever. HIS idea not MINE.”

Me and Pedro are probably going to shoot one of the most dangerous videos ever😳😳 HIS idea not MINE🙈

— Monalisa Perez (@MonalisaPerez5) June 26, 2017

Mr Ruiz had practiced and showed Ms Perez a book which had previously stopped a bullet, she said, according to the criminal complaint.

Ms Perez phoned 911 about 6.30pm on Tuesday, local time, when the bullet pierced his chest. Paramedics attempted to revive Mr Ruiz, but he was pronounced dead at the scene.

Pedro Ruiz III, 22, is pictured in an earlier video stunt. Photo: Facebook

Ms Perez, who is pregnant, was charged with second-degree manslaughter and faces a maximum penalty of up to 10 years behind bars if found guilty.

She was released on bail on a US$7,000 (A$9,100) surety.

The couple regularly filmed pranks for their YouTube account, and their family was reportedly aware of the stunt they had planned.

In their most recent YouTube video, Mr Perez could be heard saying: “Imagine when we have 300,000 subscribers.”

Mr Ruiz’s aunt Claudia said she had told him not to do it and asked him why they needed to involve a gun in their stunts, according to Valley News Live.

He told her: “Because we want more viewers.”

She said the couple had been together for six years and were in love.

“It was just a prank gone wrong. It shouldn’t have happened like this. It shouldn’t have happened at all,” she told Valley News Live.

Monalisa Perez, 19, has been charged with second degree manslaughter. Photo: Twitter