The family of a Jewish musician stabbed to death by a psychiatric patient have said they were let down by the NHS after waiting more than five years for investigations into the killing.

An inquest into the manslaughter of klezmer violinist Michael Kahan in June 2008 found this week that doctors could not have prevented the death.

At Manchester Crown Court, assistant coroner Sally Hatfield QC said it was “unpredictable and unpreventable” and recorded Mr Kahan’s death by stab wounds to the abdomen as an unlawful killing by schizophrenic Jonathan Mills, who had been released from a secure psychiatric hospital ward two weeks before.

Ms Hatfield said: “Jonathan Mills drove to an area near a synagogue with the intention of killing a Jewish person. His intention was shockingly carried out. It was not a racist killing but a symptom of his illness and psychosis. His delusion could have been about Martians or any racial group.”

She added: “I do not find any basis of substantial criticism of clinicians treating Jonathan Mills.”

The inquest, which closed on Wednesday, heard how psychiatric professionals working for the Pennine Care NHS Foundation Trust could not detect that Mr Mills had failed to take his anti-psychosis medication. He was also able to mask any violent delusions from doctors.

Evidence showed that the inquest had been delayed for five years while the NHS carried out its own inquiries.

After the inquest, Mr Kahan’s family said in a statement that “Michael’s death tore a gaping hole in our hearts and turned our lives upside down.”

“We were forced to wait far too long for answers, to remain in limbo for more than five-and-a-half years until the investigations were completed. The indifference shown us by those who should have been the first to take responsibility and offer help made the tragedy of Michael’s murder even worse.”

Dr Henry Ticehurst, medical director at Pennine Care, said: “After a thorough examination of the care provided by the trust to Mr Mills, we are reassured that there were no failings that led to this unpredictable event, which has been upheld by the coroner.”