A TEENAGE boy who stabbed his foster carer to death had witnessed a brutal knife attack on his stepfather, an inquiry has heard.

The boy told child psychologists he had been present at a mass brawl where his stepfather was struck with a machete.

The teenager stabbed his foster mother Dawn McKenzie, 34, 10 times with a knife at her home in Hamilton, Lanarkshire, when he was just 13 years old.

Gillian Sloan, a child psychotherapist who assessed the boy before the killing, told how he had become accustomed to violence and was severely damaged by his upbringing.

The boy had lived with another family before he was placed with the McKenzies in November 2010. She was killed in June 2011 at her home.

The teenager was jailed for seven years in 2012 after the Crown accepted a plea of guilty to the charge of culpable homicide on the grounds of diminished responsibility.

During a therapy session with Miss Sloan in 2009, the boy wrote about watching the machete attack on his family member and lashed out at a teddy bear which was in the room.

She told the fatal accident inquiry into Mrs McKenzie's death: "He chose to write about a terrifying incident.

"We felt he had seen and experienced a lot of violent events and had had to adjust to a rough environment because of his upbringing.

"During the session he threw a rubber at a large teddy bear. When I asked him why he did it he said 'it was looking at me'. I was a bit concerned about his state of mind. A teddy is a nice thing but he saw it as a threat and wanted to attack it."

Miss Sloan said the boy "seemed to have the weight of the world on his shoulders".

"I don't think I ever saw him smile," she said. "He also slapped himself with a ruler and tied elastic bands round his ankles. I found that unusual, it was self-punitive behaviour.

"There was the sense there was something going on we didn't know about and there was something that merited further investigation."

The inquiry also heard how the boy had attacked two pupils, including a girl, at school in 2010 and broke his hand punching a wall following a row with a previous carer.

Miss Sloan, who works for NHS Greater Glasgow and Clyde, told how she wanted further follow-up therapy sessions with the boy but he refused to attend and could not be compelled to do so.

When he moved in with the McKenzies, his social worker Steven Lorimer told her he was doing well and it was agreed he would not need any further therapy.

She added: "His early experiences had a devastating effect on him.

"They effected how he related to his peers, his siblings and to adults in authority.

"One of the things that has changed because of this case is that it is now important that children are seen directly more often."

Mrs McKenzie's husband Bryan had earlier told the inquiry they should have been given more information about the boy's background.

Mr McKenzie said if they had known more about the boy's history they would have still have taken the placement, but would have been "more cautious and better armed".

The inquiry, which is being held in Motherwell before Sheriff David Bicket, continues.