According to reports in Italy, the incident happened while she was taking part in a terrifying TikTok challenge.
The Sun UK reports that Antonella was found lifeless on the bathroom floor by her four-year-old sister in Palermo, Sicily.
She told her family she was going for a shower – but investigators are said to believe she was really filming herself for the online craze.
Antonella’s heartbroken dad Angelo said another of Antonella’s sisters told him she had been taking part in a TikTok challenge, La Repubblica reports.
He told the paper: “Antonella was playing the game of asphyxiation.
“My daughter, little Antonella, who dies because of an extreme game on TikTok, how can I accept it?”
Police in Sicily have seized Antonella’s phone and are investigating possible links to social media sites, according to reports.
Like the dangerous Blue Whale challenge, the craze Antonella is feared to have joined is a sick game that has been popular on TikTok over the past year.
Experts have warned of the risks associated with these challenges, including fainting, seizures, brain damage, and even death.
Public prosecutors in Palermo have opened two investigations for “instigation to suicide”.
Antonella’s mobile has been seized by investigators, who are looking into if she was broadcasting live, if she had been invited to play the game by someone else or if she was making the film for a friend.
Prosecutors also want to verify if she was copying videos of other TikTok users taking part in the challenge.
ANSA media agency report she arrived at the hospital in cardiac arrest yesterday.
Doctors fought to save her life but she was later declared brain dead and in an irreversible coma.
Her organs were donated to save three other children before her life support was switched off.
Dad Angelo said: “In this way, Antonella will save many children.”
TikTok said they would be fully cooperating with authorities.
A spokesman said: “Our deepest sympathies are with the girl’s family and friends.
“We do not allow content that encourages, promotes, or glorifies dangerous behaviour that might lead to injury, and our teams work diligently to identify and remove content that violates our policies.
“While we have not currently found evidence of content on our platform that might have encouraged such an incident off-platform, we will continue to monitor closely as part of our continuous commitment to keep our community safe.
“We will also assist the relevant authorities with their investigation as appropriate.”
