According to a witness, the alleged attacker was wearing what looked like a military-style helmet and bullet-proof vest.
A 20yo suspect has been charged with murder.
Four members of the family are dead and a nine-year-old is hospitalised with serious injuries.
He says he's pained by the discovery, but stopped short of a direct apology.
The discovery of the remains at a former residential school in Canada has reopened wounds for survivors of the system.
Some of the children were as young as three years old.
PM Trudeau said the news "is a painful reminder of that dark and shameful chapter of our country's history".
"I am deeply embarrassed by my actions and the distress they may have caused anybody who witnessed them."
"If I had a chance to do it all over again, this would not have happened."