A teen boy confessed to throwing a young child down a flight of stairs months before the 5-year-old died, a jury heard at a Cardiff court in Wales.

Angharad Williamson, 30, and her boyfriend, John Cole, 40, are accused of killing Williamson’s son, Logan Mwangi. An unnamed 14-year-old boy who lived in the family home is also accused of participating in the boy’s murder. The teen was 13 when the alleged incident happened.

All three defendants are currently on trial for murder and perverting the course of justice. All three have pleaded not guilty. Cole, however, pleaded guilty to perverting the course of justice.

During testimony Wednesday, prosecutors alleged that the 14-year-old, who was described as a “monster,” pushed Logan down a flight of stairs in August 2020, nearly a year before Logan’s death. Williamson, who claimed she only recently found out about it, admitted that instead of taking the boy to the hospital, she attempted to treat him herself.

“I have suffered previous shoulder dislocations and my ex-partner was able to put it back in the socket. I have then decided I could put Logan’s arm back into place,” Williamson previously told an officer, according to The Independent.

The teen is also accused of saying he wanted to not only kill Logan, but murder his entire family “The Purge” style, in reference to the popular movie that allows its characters to commit crimes legally during a 12-hour period, BBC reports.

As CrimeOnline previously reported,  Williamson claimed she woke up to find Logan missing from their home in July 2021, and added, “my back gate is open.”

“He can’t be on his own, there’s no parent with him; he must be scared,” Williamson told a 999 dispatcher while reporting the boy missing.

Investigators said the 999 call was a ruse to throw off the truth that Williamson, the 14-year-old, and Cole murdered Logan while he was quarantined with the Covid-19 virus and unable to go outside or see anyone.

Police found Logan shortly after the 999 call. He was wearing mismatched pajamas and lying deceased in a river, BBC reports. Prosecutor Caroline Rees QC said the child had “significant injuries to his internal organs and his brain which caused his death.”

“The prosecution’s case is that Logan was murdered and each of these three defendants played their part in the killing of that five-year-old child,” Rees said.

The victim was taken to the Princess of Wales Hospital, where a pathologist said he had injuries “so extreme you would expect to find them as a result of a fall from a great height or a high-velocity road traffic accident.”

Rees added that Logan has 56 external injuries caused by blunt force trauma.