BEMIDJI, Minn. (AP) — A Bemidji man has pleaded guilty to killing his ex-girlfriend, who went missing last fall.

Forty-year-old Marchello Cimmarusti pleaded guilty Monday to second-degree murder in the death of Rose Downwind of Redby. KSTP-TV reports he's expected to be sentenced Oct. 28.

Downwind was a granddaughter of American Indian Movement co-founder Dennis Banks. She went missing in October, prompting searches of the area. Her burned body was found in a shallow grave in a forest northwest of Bemidji in December.

Cimmarusti told police he accidentally killed Downwind when she fell down stairs during an argument. But an autopsy found ligature wire around her neck, and that she had been strangled.

Two of Cimmarusti's friends are accused of helping bury Downwind's body.