RCMP in northern Manitoba say they are treating the death of a 19-year-old man in Cross Lake as a homicide.

Cross Lake, Man.

Officers were called at around 6 a.m. CT Sunday to a disturbance at a large house party, where they found the man suffering from life-threatening injuries, according to police.

The man was taken to the local nursing station, where he later died of his injuries, RCMP said in a release Monday.

Four people were arrested, but then released without charges.

RCMP did not release the deceased man's name but CBC News has learned he is Austin Monias, the nephew of Idle No More hunger striker Raymond Robinson.

Robinson, who is in Ottawa with Attawapiskat Chief Theresa Spence, said Monias' death has hit him hard.

"Denial. Shock. It made me think of how life is short," Robinson said, adding that Monias was very active in organizing Idle No More rallies for youth.

"He was a vibrant young kid that was supposed to be graduating this year," he said.

Police are still investigating and have not disclosed the cause of death.

The community of Cross Lake is about 800 kilometres north of Winnipeg.