The last of three co-defendants has been convicted of helping burn the body of a Bemidji woman who was slain by her children’s father during an argument.

Brandon Rossbach, 32, of Bemidji, was found guilty Tuesday of aiding an offender, a felony, during a six-day jury trial in Beltrami County District Court. Rossbach remains jailed ahead of sentencing Dec. 20.

Rose Downwind, 31, was killed in October 2015 and considered missing for nearly two months before her charred body was found in a makeshift grave northwest of Bemidji. Downwind was the granddaughter of American Indian Movement co-founder Dennis Banks.

Downwind’s killer, Marchello A. Cimmarusti, 41, pleaded guilty in April to second-degree murder for pushing Downwind down the stairs in the home they shared. The two had three children together. His sentencing is scheduled for February.

Cimmarusti acknowledged that the two had argued, prompting her to try to take a cellphone photo of him violating a no-contact order, according to prosecutors. Cimmarusti said he pulled the phone out of Downwind’s hand and pushed his shoulder into her, sending her down concrete stairs.

Cimmarusti then contacted Christopher J. Davis, his cousin, in the Twin Cities and asked for help.

Davis and Cimmarusti buried Downwind in a shallow grave northwest of Bemidji, surrounded the body with plastic-foam cups and plastic shopping bags that Rossbach had helped purchase, then set the body on fire. Cimmarusti led authorities to Downwind’s grave in early December.

Davis, 28, of St. Paul, pleaded guilty in July to aiding an offender and was sentenced to a term of slightly more than 10 years.