A former hospital administrator stabbed his elderly father to death and tried to kill two young children to spare them from "torture and crucifixion", a court heard.
Mentally ill Suluk Ahmed, 32, from Bethnal Green, east London, quit his job just weeks before the attack on 79-year-old Jamil Ali and a boy and girl, aged two and 12.
At the time of the stabbings in August last year, Ahmed believed he was "doing the right thing, saving them from a fate worse than death", jurors were told.
Ahmed, who has been diagnosed with paranoid schizophrenia, denies the manslaughter of Mr Ali and the attempted murder of the children, who cannot be identified, by reason of insanity.
Opening his Old Bailey trial, Zoe Johnson QC said all three victims were stabbed in quick succession at a house in Tower Hamlets on August 23 last year.
She told jurors: "Mr Ahmed admits killing his father and attempting to kill (the two children) and the only issue in this trial will be a psychiatric one."
Ahmed was so "out of touch with reality", he believed his vulnerable victims were going to be tortured and crucified, she said.
Before the attacks, twice married Ahmed was regarded as an "ordinary outgoing man" who got on well with his father, she said.
He had worked as an administrator at St Mary's Hospital in London for five years but about a year before the stabbings, a new manager was appointed who he felt bullied him, the court heard.
He took sick leave and was prescribed anti-depressants by his doctor before returning to work in July last year.
But by then, he felt he was being "persecuted" and he became "paranoid and anxious", believing his computer had been hacked and the manager wanted to blow him up, jurors were told.
A few weeks before the stabbings, he resigned from his "beloved" job and his second marriage also ended as Ahmed thought his wife was in "cahoots" with the manager, Ms Johnson said.
On August 23 last year, paramedics went to a house in Tower Hamlets where they disarmed Ahmed, who had tried to stab himself as well as his three victims, the jury was told.
The toddler had a chest wound, just centimetres from his heart, and the older girl had suffered two stab injuries to her back.
Mr Ali had been knifed in the heart and was discovered lying in his bed, the court heard.
Ms Johnson told jurors that two psychiatrists had agreed on Ahmed's mental state and would give evidence in the trial.
If Ahmed is found not guilty of the charges by reason of insanity he is likely to be made the subject of a hospital order.
The trial was adjourned until Thursday.