Michigan mom, 2 boys found frozen to death; girl knocks on door and says her "family was dead in a field," sheriff says

A Michigan mother and her two children were found frozen to death over the weekend after the mom experienced a "mental health crisis," a county sheriff said Monday.

Monica Cannady, 35, "believed someone was trying to kill her and that everybody was in on it" before she and her children died, Oakland County Sheriff Michael Bouchard said in a Monday news conference.

Authorities found the sons, ages 9 and 3, and their mother on Sunday in a wooded area of Pontiac, which is around 20 miles northwest of Detroit.  Bouchard confirmed the cause of death was hypothermia, CBS Detroit reported.