Craig Mulligan had been taken in by foster carers for eight weeks but they were unable to cope with his scary behaviour and he was allowed to return to Logan Mwangi's home
He also had a history of "cruel" attacks on young children, vulnerable adults and small animals and was trained in martial arts.
One foster carer said: "He was pure evil and enjoyed causing anxiety and fear. He knew no boundaries."
Mulligan had previously been taken in by foster carers for eight weeks in June and July 2021 but they were unable to cope with his scary behaviour and he was allowed to return to Mwangi's home.
Bridgend Social Services were aware that the foster family had been unable to cope with his behaviour.
After fostering 80 children over almost 50 years it was the first time the foster family had asked for a child in their care to be removed.
They had always done long term fostering but they were asked by the council to take in the teen for two months.
However, the teen soon showed his nasty side and on the first night showed their daughter a vape and a knife and they would regularly find knives hidden behind his pillows.
Mulligan was then moved into the family home just five days before the
murder - a cruel fact described as "not a coincidence" in court.
His tragic move was approved by a family court judge after it was supported by Mulligan's social worker Debbie Williams.
Craig Mulligan had been taken in by foster carers for eight weeks but they were unable to cope with his scary behaviour and he was allowed to return to Logan Mwangi's home before the boy died
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