Police found Mr Killen “shaking uncontrollably” A teenager stabbed a neighbour to death after seeing the man fatally stab his mother at their home in Hertfordshire, a double inquest has heard.
The hearing has been told James Killen, 18, was getting ready for school in St Albans on 30 April when he heard his mother Sandra Crawford, 53, scream.
He found Ms Crawford being stabbed by next-door neighbour Jonathan London.
Mr Killen wrestled the knife from him and stabbed 47-year old Mr London 16 times, the inquest heard.
Mr London died at the scene from a punctured lung while Ms Crawford, who staggered onto the front lawn, died in hospital eight days later from chest and neck injuries.
In the months leading up to the incident, Mr London had been complaining of hearing noises in his head and on 29 April was taken to his GP and then to hospital by his family.
He was given a blood test and sent home, the inquest heard.
Psychiatric nurse Jocelyn Cusack, who saw Mr London that day, said his family was anxious that he stay at home.
She said he was delusional and it was one of the worst cases she had seen in 20 years.
Psychiatrist Dr Seshni Moodliar said she felt he did not pose a threat to himself or others.
A mental health team was due to see him at home at 1130 BST on 30 April, but at 0830 BST he left the house he shared with his elderly parents in Sherwood Avenue and attacked Ms Crawford.
Police officer Claire Moy, who attended the scene, told the inquest Mr Killen was “shaking uncontrollably” and kept asking after his mother.
Describing what Mr Killen had told her, she said: “He saw a man punching her (Ms Crawford) and screaming ‘die, die’.”
The hearing was told he got a knife and stabbed Mr London “a few times” but the man continued to attack his mother, who he realised was in “real danger”.
Mr Killen was arrested but no charges were brought against him.
The hearing continues.
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