A string of serious failings in the care provided for a man with schizophrenia who killed his father an hour after absconding from a psychiatric ward contributed to the death, a coroner has ruled.

Coroner Kirsten Heaven also said that security systems at the hospital where Daniel Harrison was being detained were inadequate and played their part in events leading to the killing of retired chest consultant Kim Harrison.

The inquest in Swansea heard that Daniel Harrison, a carpenter, suffered from delusions, believing his family were evil and he was being targeted by drug cartels, motorbike gangs and phone hackers.

His condition deteriorated after he weaned himself off anti-psychotic drugs when Swansea Bay University health board failed to put in place the appropriate services for him and, at one point, police warned that it was only a matter of time before he hurt a relative.

His family desperately tried to get him help but one of the key mental health professionals involved in his case concluded that his chaotic state stemmed from a desire to live an “alternative lifestyle” rather than because he was very ill.

Harrison punched, kicked and stamped on his 68-year-old father at his home in Clydach, Swansea, after slipping out of a ward at Neath Port Talbot hospital in March 2022. He admitted manslaughter by reason of diminished responsibility and a judge imposed hospital orders under the Mental Health Act, meaning he would be detained indefinitely.

In a highly unusual move at the start of the inquest, Daniel Harrison appeared via video link from the unit where he is being treated and read out poems in honour of his father and said he knew his father would be “so relieved” to see the progress he was making.

The coroner said in a narrative conclusion that, at the time of the assault, Daniel was suffering from untreated schizophrenia that caused him to have paranoid delusions about his father.

She said in 2009 Harrison was “wrongly removed” from the care of the community mental health team. When in 2018 a consultant who had been treating him left their post, Swansea Bay University Health Board (UHB) “failed to put in place appropriate and timely follow-up arrangements”. Heaven said: “This contributed to Kim’s death.”

Harrison weaned himself off medication “in an unmanaged and unmonitored way” and the risk to himself and others began to increase.

The coroner said: “Daniel’s parents consistently raised with Swansea Bay UHB and the city and county of Swansea AMHP [approved mental health professional] service concerns about Daniel’s deteriorating mental health. Swansea Bay UHB clinicians and the AMHP service did not pay sufficient attention.”

Daniel was admitted to hospital on 2 March 2022 after behaving in a psychotic manner in the family home and being confrontational to his parents. While there, his risk assessments were not fully completed and his family’s concerns were not fully recorded. There was no clear plan for him in place.

On 12 March he absconded through a door that was being held open by member of staff. Heaven said: “The security systems in place were not fit for purpose,” and highlighted a “lack of adequate training”. The coroner said: “This system failure contributed to Kim’s death.”

Swansea Bay UHB said: “We offer our unequivocal apologies for our failings in this case, and are determined to learn and do everything possible to avoid anything like this happening again.”