Inquest hears disturbed 31-year-old man who had threatened his mother slit his own throat before police could reach him.
A man was able to flee from police and cut his throat, with fatal results, after a taser gun failed to stun him.
Despite an officer firing the weapon at Justin Petty, only one of the barbs was able to make contact. The other simply flew into the breast pocket of his shirt with the result that no electrical circuit was established.
It allowed Mr Petty to run inside his home and climb into the loftspace above the landing, where he slit his throat open with a kitchen knife.
Officers who went into the house to find him realised he was in the loft when they saw blood trickling through the hatch.
At an inquest on Tuesday into Mr Petty's death, Coroner David Morris was told how armed officers had rushed to the house he shared with his mother after receiving reports he had threatened to kill her.
Justin, 31, lived with his mother June, 71, at their home in The Spinney, Goldington, Bedford.
He had a history of mental health problems and, in 2006, had been sectioned under the Mental Health Act because of his behaviour and threats he had made to members of his family.
Mr Petty had eventually been discharged, but the inquest at Bedford heard that in the months that followed he refused to take his medication or avail himself of the professional help being offered.
The court was told how, on the evening of Saturday, January 19 this year, he was at home with his mother in the front room watching TV.
During the day he had been hyperactive, and was behaving in an overly affectionate manner towards her, but suddenly told her, "I am sorry mum, I have to kill you and then myself."
When she asked him why, he told her, "Because they told me to."
With that, he went into the kitchen and returned with a large knife, which he held against her throat.
The court was told she managed to escape and ran to the home of a neighbour, Terrence Banthorpe, telling him, "Can you help me, my son is trying to kill me."
Outside in the street, Mr Banthorpe saw her son brandishing a large knife.
As Mr Petty began to walk towards the neighbour, knife in hand, he saw Mr Banthorpe's Rottweiller dog and went back inside.
Police were called and, because of the knife and Mr Petty's threats, armed officers were deployed around the house.
Eventually, the court was told, Mr Petty opened the front door and sat on the threshold, still holding the knife and bleeding heavily from two wounds to his chest.
Asked to put the knife down and move away, he refused, whereupon an officer fired a taser stun gun.
Because one barb failed to make a proper connection, Mr Petty was not stunned and retreated back into the house.
By the time officers went in, he was hiding in the loft, having cut his throat open.
The court was told that, on seeing blood trickling through the hatch, police officers decided to heave open the loft hatch. It was not an easy task, as Mr Petty was lying on it on the other side. As they tried to bring him back onto the landing floor, he was struggling and resisting their attempts to help him.
Handcuffs were applied and leg restraints, but still he continued to struggle.
He was rushed by ambulance to hospital and, on the way, suffered a cardiac arrest.
At Bedford's South Wing Hospital, he underwent emergency surgery but, early on Sunday morning, died.
The cause of death was given as incised wounds to his neck and stab wounds to the left side of his chest.
The heart attack he had suffered in the ambulance had been due to the heavy loss of blood.
Det Insp Robert Gardner, with Bedfordshire Police's professional standards department, who conducted an investigation into the handling of the case, said that when the taser gun had been fired, only one of the two barbs had made a connection with Justin's clothing. The second was simply hanging loose in a breast pocket.
The court was told at the time the officer fired the gun Justin had been sitting down on the threshold of the house, rocking to and fro, and it was probably as he moved forward that the barb flew into his pocket.
Coroner Mr Morris was told that police had decided to use a taser because it was considered a less lethal option.
The Coroner told the court that he didn't see Justin as suicidal, but said his verdict would be that he died from self-inflicted injuries while the balance of his mind was disturbed.
He added that, having heard the evidence, it was clear there had been no failure by the police, the hospital where Mr Petty was taken to or the ambulance service in the way they dealt with him that night.
Mr Morris said despite the fact that Mr Petty would not take his medication he had been able to manage in the community for "quite a long time."
The inquest heard that the officers who had got Mr Petty out of the loft that evening and then tended his wounds thought they had saved him and were disappointed and upset when they learned later that he had died.
After Mr Petty had been admitted to the Weller Psychiatric Wing at Bedford Hospital in February 2006, he had been diagnosed with schizophrenia.