The British Independent Police Complaints Commission has begun an investigation into the handling of the manhunt for Raoul Moat by Northumbrian police.
Part of the investigation will focus on when and why two Taser stun guns were discharged during the six-hour stand-off last night.
The force's handling of the case has been under the spotlight ever since the fatal shooting of Chris Brown and the woundings of Moat's ex-girlfriend Sam Stobbart and Pc David Rathband last weekend.
The IPCC is already investigating whether the police responded adequately to a warning from Durham Prison that Moat might intend to cause serious harm to Miss Stobbart.
Moat was freed from the prison on 1 July, after serving a jail term for assault and the prison issued the warning the following day.
Northumbria Police Temporary Chief Constable Sue Sim stressed that the warning did not suggest Moat intended to shoot or kill Miss Stobbart, but questions were asked about whether the force should have done more to protect her, which may also have prevented Mr Brown's tragic death.
Apprehending Moat sooner could also have prevented the shooting of Pc Rathband. He was apparently targeted because Moat had a grudge against the police, which was exacerbated when frightened Miss Stobbart falsely told him that her new boyfriend was a police officer.
No shots were fired by the police during the stand-off. They had negotiated with Moat to try to get him to give himself up.
He shot himself in the head early this morning after being discovered on a river bank yesterday evening.
An eyewitness told the Press Association the siege came to an end when police surrounded the former nightclub doorman and jumped on him.
A single gunshot was heard before the 37-year-old was taken by ambulance to Newcastle General Hospital.
On arrival, he was seen being taken from the ambulance on a stretcher with a blanket covering his head. It is believed he was pronounced dead on arrival.
A post-mortem examination gave the cause of Moat's death as gunshot wounds consistent with the weapon he was carrying.
Moat's death brought to an end a huge manhunt involving police officers from 15 forces, Scotland Yard sharpshooters and armoured 4x4 cars.
The drama began at around 7.20pm yesterday when police responded to reports Moat was on the riverside.
Officers warned people to stay indoors for their own safety as they surrounded the fugitive, who witnesses said was lying on the ground with a sawn-off shotgun pointed at his head.
Paul Gascoigne offers his support
At one point former England footballer Paul Gascoigne turned up in Rothbury to offer his support to Moat.
A clearly intoxicated Mr Gascoigne gave a radio interview and said he had brought him a 'can of lager, some chicken, a mobile phone and something to keep warm'.
As the siege wore on Moat apparently relaxed and allowed police to bring him food and water.
But at about 1.15am, with heavy rain lashing down, officers apparently attempted to wrestle Moat to the ground and he shot himself.
The Independent Police Complaints Commission has said that police involved in the stand-off are understood to have fired a Taser stun gun during the operation.
Chief Superintendent Mark Dennett of Northumbria Police said: 'Police discovered a man fitting the description of Raoul Thomas Moat at around 7pm near the riverbank in the vicinity of Rothbury.
'When he was discovered he was armed. Expert negotiators were brought in to speak to him and spoke to him extensively for several hours.'
In letters left for officers earlier in the week he claimed to be a 'killer and a maniac' and pledged to keep shooting police until he died.
Initially it was believed Moat posed a serious risk only to his former girlfriend and police officers. He held a series of grudges against the police and was only released from a short spell in prison on 1 July.
But on Thursday police warned that Moat had made threats against the wider public.
The focus of the hunt turned to the small town of Rothbury - 50km north of Newcastle - on Tuesday after a car linked to Moat was found abandoned.
Police have been stationed outside schools and people who live in the area warned to keep windows and doors locked.
Also on Tuesday Karl Ness and Qhuram Awan - originally thought to be hostages - were found wandering along a country lane.
Both have since appeared in court charged with conspiracy to murder.
