A grieving woman says her 23-year-old brother was shot dead by police on Long Plain First Nation Tuesday night.

"They went rushing in there. Everything happened too quick," Patricia Richard said her mom told her.

Richard identified her brother as Ben, who lived with their mother on the Manitoba reserve, about 100 kilometres west of Winnipeg.

"She's taking it pretty hard," Richard said about her mom, stopping to choke back tears.

"She said they didn't have to [shoot him]. He wasn't threatening anyone, he just snapped on himself."

Manitoba's police watchdog said a team of investigators was deployed to Long Plain Tuesday night examining what it called a "serious incident."

The Independent Investigation Unit of Manitoba released a statement Wednesday afternoon announcing it had opened an investigation into the fatal shooting of a 23-year-old man in Long Plain.

Officers responded around 6 p.m. Tuesday to a report of a man armed with a gun, the investigation unit said.

"A confrontation took place between the man and police, resulting in one or more officers discharging their firearms and striking the man. He was pronounced deceased at the scene," the IIU's release said.

The Independent Investigation Unit investigates all serious incidents involving police officers in Manitoba, whether occurring on or off duty.

'I just think everything got to him,' sister says

Patricia Richard, who lives in Winnipeg, was contacted Tuesday evening by her mom, who was worried about Ben, saying he was shooting a gun in the house and had blown out all of the windows.

"I don't know what set him off," said Richard, who could hear Ben in the background "freaking out" as she spoke with her mom.

"We've had a lot of deaths in our family and lost one of our close cousins. I just think everything got to him."

The Manitoba First Nations Police, formerly known as the Dakota Ojibway Police Service, is headquartered on Long Plain and provides policing in six Indigenous communities in the province. (Manitoba First Nations Police)

Long Plain is the headquarters for the Manitoba First Nations Police, which provides policing in six Indigenous communities in the province.

Richard is questioning why police did not set up some type of perimeter and take time to speak to Ben. The officers acted too quickly, she said.

No one from the MFNP responded to requests for an interview.

The chief of Long Plain deferred comment to the RCMP, who then deferred comment to the IIU.