The allegation was made in a preliminary report by the Acimowin Opaspiw Society (AOS) looking into unmarked and undocumented graves at the former Blue Quills Residential School. The report was released at a press conference.
"The investigation has received disclosures from intergenerational survivors, whose parents witnessed homicides," the report states.
The homicides were allegedly committed by a man referred to as a "disciplinarian" who worked at the school from 1935 to 1942. It is said he pushed boys down stairs, killing them, and then threatened other boys who witnessed the murders that he would kill them if they told anyone.
He died in 1968.
Documents uncovered by the investigators showed that 215 students aged 6 to 11 died at the school, which was operated at two different sites -- from 1862-1898 at Lac la Biche, Alberta, and from 1898 until 1970 at Saddle Lake, Alberta. Both were run by the Roman Catholic Church.
The Saddle Lake Cree Nation formed the AOS group in 2021 to investigate the missing children. They believe about 215 undocumented burials of children are at the Sacred Heart Cemetery in Saddle Lake.
"The investigation's theory regarding the missing children of the Saddle Lake site is that they are buried in undocumented mass graves," the report states.
Investigators believe children were also killed by being deliberately given unpasteurized milk contaminated with bovine tuberculosis, said AOS executive director Leah Redcrow.
"How I know it's deliberate is because the school administrators weren't dying, the children were. And the school administrators didn't eat the same food as the children," Redcrow told reporters.