Yellowstone's Mo Brings Plenty questioned why his nephew Cole Brings Plenty's death has gone "uninvestigated" after no foul play was found. Nearly two years since Cole's death, Mo, 56, reflected on how "heartbreaking" the loss has been. "He was my nephew, but he was like a son to me. And for his murder to go uninvestigated, and for it to be written off as 'no foul play,' because they didn't want to invest anything into it? It's heartbreaking," Mo claimed in an interview with The Hollywood Reporter on Sunday, March 22. "Because we're taxpaying people as well.