Who raised two abandoned children? ND 1884

I have since 2006 heard about a tragedy happened in Grand Forks, ND in the fall 1884. It was a family of 5, mother, father and 3 children, mother was in high pregnancy with the 4th baby. They arrived America two years before the tragedy happened. In end of August 1884 father killed mother, and a couple of days later he killed himself. Father was Knut Anderson Moe, mother Inga Moe. 3 children left alone. The oldest girl was Marie (Mary?), she was born Nov 23 1878 Then Martha, she was born June 21 1880, but I have located all the information about her. Her descendants have no ideas about her siblings. Then Anders/Andreas/Andrew, he was born February 16 1882. So the question is, where was Marie and Anders raised? I have tried many different ways to locate them, but until now, nothing have been a success. There is no info to locate in the probate records, so the only solution I have, is that maybe, maybe, someone have heard about this tragedy, and about the children. Maybe some old people from the area Grand Forks