BROOKS, Alta. - Witnesses say that a southern Alberta man was acting erratically before RCMP tried to subdue him with a Taser, an investigator said Thursday.

Grant William Prentice, 40, of Brooks, Alta., died Wednesday after police deployed the Taser and then physically subdued him during an investigation into a disturbance in a residential neighbourhood.

Clifton Purvis, a spokesman for the Alberta Serious Incident Response Team -- which investigates serious incidents involving police -- said that eyewitnesses reported that a bloodied Prentice was seen approaching people in the area.

"At one point (he) attempted to forcibly enter an occupied dwelling house," he said.

There were media reports that neighbours saw a seemingly disoriented man staggering along the street.

Emergency medical services had been dispatched to the scene because Prentice had suffered some undetermined injuries before his contact with police and witnesses said he was bleeding, Purvis said.

Two officers initially responded to the incident around 7:30 p.m. and then two more were later called for backup, Purvis said.

"During the course of dealing with him, the RCMP attempted to deploy a conducted energy device. At this point I'm unable to say whether that deployment was successful," he said.

The agency is still investigating whether the dart from the device made contact with Prentice's body, Purvis said.

An autopsy Friday may help determine that, he added.

After officers used the device to try to subdue the man, they physically restrained him, Purvis said.

"He eventually, after being physically restrained, was handcuffed. He was noted to be in medical distress and taken to hospital," he said.

Prentice was later pronounced dead.

Purvis would not comment on how Prentice may have come to be injured.

He said that Prentice was known to police, though wouldn't elaborate.

The agency will look into whether the Taser or the way in which Prentice was restrained may have been factors in his death, the investigator said.

RCMP offered few specifics about what happened, saying the investigation was now the responsibility of the independent agency.

"We certainly regret the outcome of this incident," said Sgt. Patrick Webb, a spokesman for the RCMP in southern Alberta.

"We'd like to offer our condolences and support to this family as they're dealing with this loss," he said.

Martin Shields, mayor of the community of about 14,000 southeast of Calgary, said he's known Prentice's family for about 30 years.

He said Grant Prentice had worked at several jobs in the community and believed his most recent one may have been in the oilfield services sector.

Prentice's death came as a personal shock and has been a blow to relatives, he said.

"As any family would be with the loss of a child, sibling, they are very upset."

Shields confirmed the dead man is a relative of city councillor Bill Prentice, but would not say how the two are related.

An unidentified woman who answered the phone at Prentice's residence said that the family is not commenting at this time.

Brian Mason, Alberta's NDP leader, denounced this latest death, and called on the province's Solicitor General to stop the use of Tasers altogether.

"Enough is enough. It's time for a ban on Tasers," he said.

He said the devices were originally to be used instead of lethal force.

But Mason said some officers are now using them as an alternative to physically subduing someone, or as a way to force people to obey police orders -- sometimes with fatal consequences.

"I think the time has come to end the use of Tasers in this province. That's what Newfoundland has done, and as far as I'm aware, they're coping just fine."

Fred Lindsay, the province's solicitor general, defended the use of Tasers and said police will continue to use them.

"It's a tool that's very effective in helping police make arrests and protects both police and the public," he said.

He said he's seen little evidence that such devices have caused deaths in Canada.

Police use of Tasers has come into question since the death of Robert Dziekanski at the Vancouver airport in October 2007.

The Polish man died after being stunned with a Taser during a confrontation with Mounties at the international arrivals area of Vancouver airport, where he'd been throwing furniture.

He'd wandered around lost for hours in the passengers-only area before the confrontation with police, unable to find his mother.

Alberta recently mothballed 50 Tasers after tests showed they weren't working properly.

The rejects made up 12 per cent of the 412 devices tested. There were not problems with the remaining 88 per cent.