This the timeline I imagine:
Bobbi Jo goes to 4077 to feed the chickens and dogs sometime well before 7:49am
She finds the door locked, use the spare key and finds CR1 and Gary dead
She calls her dad and brother, or dad and then brother.
Leonard or James comes to 4077
James or Leonard, whichever doesn't go to 4077, checks out 3122, perhaps after trying to call them and getting no response.
Bobbi calls 911
James/Leonard calls Bobbi and Leonard/James back and reports that "they got Dana, Hanna May, and CR2 too".
Whoever is with Bobbi goes next door to 4199 and finds Frankie and Hannah Hazel dead.
LE arrives
Donald Stone hears/sees news on the TV and checks on Kenneth at 799 Left Fork. Maybe he checked on other Rhoden cousins too, maybe not, but wouldn't we all like to know if he did.