A paranoid schizophrenic stabbed his wife's stepfather to death 11 days after being discharged from a mental health hospital, a court heard.
Richard King, 35, of Wells, Norfolk, killed John West, 61, at his home in Sheringham, Norfolk, on 7 August 2004.
At an earlier hearing King admitted manslaughter due to diminished responsibility.
On Monday at Ipswich Crown Court he was sentenced to indefinite detention in a secure mental health unit.
Defence barrister Russell Flint told the court that King had received treatment for mental health problems since 1989. He was most recently admitted to hospital on 15 July 2004, but had returned home four days later against doctors' advice.
Before killing Mr West, King was last seen by a community mental health nurse who reported that King was making threats to himself rather than to others.
Prosecutor Graham Parkins QC told the court that, on 6 August, King told his wife Jane he was going to kill her stepfather before arming himself with a kitchen knife and driving to Mr West's home.
Mr West was discovered outside his home by his partner, Mrs King's mother, Jean Craske. A post-mortem examination revealed he had died from multiple stab wounds.
Judge John Devaux said that although King was discharged 11 days before Mr West's death, there was no criticism of anyone involved in the case.
He told King: "There is a real danger you will be violent to some other person at some time in the future."