A boy who lured a 14-year-old girl to a park and inflicted "incomprehensible" violence upon her has been found guilty of murder and rape.
Viktorija Sokolova's head was "smashed in" with a hammer-like object in a "sustained and ferocious" attack.
Her lifeless, partially clothed body was found dumped on a bench in Wolverhampton's West Park the next day.
The 16-year-old boy, who cannot be named due to his age, denied murder but was convicted after a three-week trial.
Jurors at Wolverhampton Crown Court unanimously found the defendant guilty of murder and rape, but were directed to clear him of a further charge of sexual penetration of a corpse.
Lithuanian-born Viktorija went to the park late at night on 11 April after her killer contacted her via Facebook Messenger, the court heard.
Once there, the pair met at a pavilion referred to as the "black house", where Viktorija was struck over the head at least 21 times, causing multiple fractures to her skull and spine.
The boy raped her and dragged her 150m across the park, where he left her draped over a bench.
Police said the assault was so violent they found three of the schoolgirl's teeth and an earring, ripped from her ear, in the blood-spattered pavilion.
A dog walker found Viktorija's body the next morning, initially mistaking it for a blow-up doll left in the park as a "prank".
The court heard her killer had claimed the pair had consensual sex and she was "alive and well" when he left to go home.
But he was caught on CCTV as he attempted to cover up what he had done by hiding clothing and hurling his victim's phone towards a lake.
The "forensically aware" murderer hid the mobile phone he used to contact Viktorija behind a wardrobe, police said.
In the hours after the killing, he used his brother's phone to search "how to delete your Facebook account permanently" and also filmed himself scrolling through the Notes app on his iPhone as he prepared to delete evidence.
The recording was of such high quality, detectives were able to use the clip to match a fingerprint left on the screen to the defendant's.
Despite the mobile phone evidence, the boy's barristers had suggested Viktorija's parents may have played a part in her death, after it emerged microscopic traces of her stepfather's semen were found in her underwear.
But the pair were eliminated from police inquiries at an early stage, and forensic experts suggested the transfer of her stepfather's DNA was via innocent means.
Justice Jeremy Baker warned the teenager, who will be sentenced on 22 February, there was "only one sentence" he could impose.
The judge said he was "obviously concerned as to the extreme nature of the offences in this case" and has ordered a pre-sentence psychiatric report.
'I keep asking God why this happened'
During his defence Viktorija's killer declined to take the witness stand - claiming to be suffering from learning difficulties.
But his barristers accused her mother, Karolina Valantiniene, and stepfather, Saidas Valantinas, of murdering the teenager.
Mr Valantinas said he had no idea why his DNA was on her clothing and said the defence's argument was "unreasonable", "unsubstantiated", and "rude".
The court also heard about his "turbulent" relationship with Viktorija, who was sent to live with her father in Northern Ireland for two months because she repeatedly ran away.
Jurors were told there was also a physical altercation between Viktorija and her mother the Sunday before her murder.
During the trial, Ms Valantiniene said, the murderer never looked at her, "maybe because of him feeling ashamed".
"This is beyond comprehension that something like that has happened to us," she said. "I keep asking God why and for what this happened to us."
Det Insp Caroline Corfield said there was "nothing" in the defendant's background to suggest he would "commit a seriously violent act, let alone the inexplicable levels of violence involved in Viktorija's murder".
The pair had been friends, she said, emphasising her killer was not a "faceless person" she met online.
"Viktorija could never have imagined someone she knew and trusted would betray her trust in the way he did," she said.
Wolverhampton Safeguarding Board has said it would publish a serious case review next year looking at Viktorija's contact with the authorities "to establish whether any lessons can be learned".