Investigations into the actions of Northumbria police in the hours before the death of Raoul Moat are concentrating on two Taser shots fired at the fugitive before he killed himself.

The Independent Police Complaints Commission will ask if the 50,000-volt charges from the stun gun prompted the former bouncer to fire his shotgun on himself after a six-hour confrontation with police.

The IPCC announced an official inquiry into the final moments of the standoff between armed officers and Britain's most wanted man within hours of Moat's death.

IPCC investigators began arriving in the town of Rothbury today to try to piece together the final moments of Moat's life.

Nicholas Long, an IPCC commissioner, said the inquiry would seek to ascertain "how this incident came to a conclusion".

No gunshots are believed to have been fired by police during the confrontation.

The IPCC is also looking at the failure of Northumbria police to act on information from Durham prison that Moat was a possible danger to his former partner Samantha Stobbart, 22, who had ended the relationship while he was in jail. Two days after his release on 1 July, he shot and wounded Stobbart and killed Chris Brown, 29, her new boyfriend. The following day Moat shot David Rathband, 42, an officer from Northumbria police, in the face.

Fresh details about Moat's background have emerged, which may explain his enmity towards the police. Arrested 12 times since 2000, Moat had been charged on seven occasions, but convicted only once – for assault on a child, for which he served his recent prison sentence. In 2000 he was arrested on conspiracy to murder in relation to a Newcastle gangland killing, but was released without charge.

As the inquiry got under way, Northumbria police's acting chief constable Sue Sim admitted that a Taser stun gun was fired at the 37-year-old, but "did not prevent his death". Later, the IPCC also said Taser stun guns were discharged during the police standoff.

Although Tasers are designed to incapacitate criminals, medical experts say they can trigger involuntary muscle spasms in people.

Moat had spent most of the confrontation holding his sawn-off shot gun to his head and neck, before squeezing the trigger at 1.15am. This followed hours of gentle persuasion by police negotiators to give himself up in an attempt to bring to an end one of Britain's most extraordinary manhunts.

Investigators will be looking at the account of Susan Ballantyne, a Rothbury resident, who described how police officers had crowded around Moat in the moments before he shot himself. They will also look at Moat's police history.

The father of three had evaded capture for six days. Before Saturday's shooting in Rothbury, Northumbria police had repeatedly insisted that they wanted to take Moat alive. Sim said officers had been "striving to persuade" the gunman to give himself up peacefully.

Other areas that the IPCC may choose to investigate include the response times to releasing information to the public. A positive sighting was made of the distinctive Lexus saloon used by Moat in Rothbury a week ago.

Christa Tocer said she noticed the car parked near the Coquetvale Country House hotel – opposite where Moat died – on Saturday, 3 July. She noticed the car parked there again 30 hours later on Sunday night, shortly before PC Rathband was shot. Police, however, did not reveal details of the car until a press conference on Tuesday morning.

The inquiry into Moat's death may also raise questions over the surveillance strategy of Northumbria police. Before arriving in Rothbury last Saturday, Moat visited his friend Andy Mcallister in Newcastle.

Homicide detectives spent much of Sunday interviewing Mcallister, 45, but did not keep him under close watch. At 1.30am on Monday, 5 July, Moat handed a 49-page handwritten confession to Mcallister for the police, and sought to tell the media his side of the story.

More embarrassing to the Northumbria force are the concerns from Rothbury residents at how police managed to miss Moat, despite allocating 200 officers and the resources of 15 forces to the manhunt.

Signs are emerging that Moat may have used a network of underground storm drains running beneath the town to avoid capture. The network would have granted him access to drains straight into the high street.

Several witnesses saw Moat on the high street on Thursday at about 11am, the night before the fugitive was apprehended as he walked towards the centre of Rothbury with his shotgun.

Chief Superintendent Mark Dennett said yesterday that signs indicated that Moat was "always on the move" during last week's hunt.

A postmortem examination will be carried out to confirm the cause of Moat's death and what sort of gunshot wound he suffered.

The continuing police investigation may yield further charges. So far two men, Karl Ness, 26, and Qhuram Awan, 23, both from the north east, have been remanded in custody accused of helping Moat. The two have been charged with conspiracy to commit murder and possessing a firearm with intent.

Three men and a woman – all from Rothbury and the surrounding area – have been arrested on suspicion of assisting an offender.