Image copyright YouTube Image caption "They were in love, they loved each other," Pedro Ruiz's aunt said of the aspiring YouTubers

Monalisa Perez, 19, and her boyfriend Pedro Ruiz, 22, wanted to be famous on YouTube.

But until a dramatic stunt on 26 June involving a gun and a hardcover book that left Pedro dead, there was little indication in their videos how far they were prepared to go in order to attain online celebrity.

The couple from the US state of Minnesota had been uploading videos for less than two months documenting their everyday lives.

Though they had filmed some minor pranks - Monalisa dusting a donut with baby powder before feeding it to Pedro, for example - they seemed relatively harmless.

In one video filmed in a hospital, they learn their new baby is going to be a boy.

"Imagine when we have 300,000 subscribers," Monalisa pondered in a video uploaded at a fun fair on the day Pedro was killed. "People will be like 'oh my god, hi!'"

Now she faces a second-degree manslaughter charge over a reckless stunt that was said to be her boyfriend's idea to boost their profile. She fired a Desert Eagle handgun from close range, as he held an encyclopaedia in front of his chest.

He had experimented previously and thought the thick book would protect him, but the couple's three-year-old child and nearly 30 onlookers watched as she fired a fatal bullet.

Image copyright Twitter/@MonalisaPerez5 Image caption She told police the stunt had been Ruiz's idea, and that he had to convince her to do it

Since YouTube launched in 2005, it has attracted people willing to do things on camera for a slice of minor online fame.

But in 2012, the company made it easier for contributors to obtain a chunk of the advertising revenue they generate from videos. Studios were created and grants given out to groom a stable of stars who need to make fresh, compelling content to keep the clicks - and advertising dollars - rolling in.

They are often media personalities in their own right, with agents and slickly produced videos.

Hundreds of thousands of others, like the Minnesota couple, sit below them and are trying to gather followings. Many have little success.

But the rewards of becoming one of the few who make it big can be a huge motivation to keep trying. (According to Forbes, the top 12 highest-earning YouTube stars made a combined $70.5m from June 2015 - June 2016.)

And while stunts are merely one genre of an extremely diverse landscape of videos made by YouTubers - from cooking to comedy and music to beauty - they do get millions of views.

'Most horrific I've seen'

Dr Arthur Cassidy, a British psychologist specialising in social media, says videos of dangerous stunts can inspire teenage copycats who "haven't got the cognitive function to figure out this could be very fatal".

"It's perceived as being 'fun' or 'exciting' or 'high-risk'. Anything that is high risk is intriguing, gets adrenaline going and sets up highly competitive game playing within the fraternity of late adolescence."

But what the Minnesota couple tried to film is "one of the most horrific cases" he has come across.

Fears that young people watching from home could try it, but with a less powerful weapon to see if it could work, are "salient and highly profound", Dr Cassidy says.

Social crazes

Doing dangerous things for online attention is nothing new.

In 2011, Australian Acton Beale fell to his death after trying to "plank" on the balcony of a seventh floor flat in Brisbane.

The planking craze - which involved people lying down straight-bodied in unusual, but mostly safe, places - was largely confined to still images uploaded to Facebook.

But the Australian case signalled how a growing internet "stunt" culture for attention could lead to tragedy, and since then several online trends have reportedly caused deaths worldwide.

Image copyright Alexander Chernikov Image caption Russian Alexander Chernikov set his trousers on fire before jumping into snow. Video of the stunt went viral

Of course, YouTube has no borders, and stunt videos from anywhere can go viral globally.

Russia's Interior Ministry recently launched a "safe selfie" campaign in response to a growing local culture of amateur daredevils filming their stunts.

In one video watched by millions of people, Alexander Chernikov lights his trousers on fire and jumps off a nine-storey building into the snow.

These kinds of stunts make the antics of TV pranksters from a pre-YouTube era, like those of the MTV reality show Jackass, seem tame.

Critics say that YouTube, owned by Google, needs to do more to take down videos of extremely dangerous stunts.

The company said it was "horrified to learn of the tragedy in Minnesota" and that its thoughts were with the family. No video of the incident is believed to have been uploaded.

A spokesperson told the BBC that it removes content flagged by users that breaks its rules.

Its policy on harmful and dangerous content says it draws the line at content "that intends to incite violence or encourage dangerous or illegal activities that have an inherent risk of serious physical harm or death".

Examples of what would be banned include videos depicting "bomb making, choking games, hard drug use, or other acts where serious injury may result".