Jimmie Johnson In-Law's Murder-Suicide Police Body Cam, Gunshot Heard

"SHOTS FIRED"

Eerie police body cam footage has emerged from the response to the home of NASCAR superstar Jimmie Johnson's in-laws ... revealing his mother-in-law shot herself just as officers arrived.

In the video, obtained by TMZ, officers approach the home of Dr. Jack Janway and his wife, Terry Janway. Cops observe Jack through a window, deceased from a gunshot wound and covered with a blanket. They open the front door, announce their presence and another gunshot is heard from inside the home.

Cops say that shot was from Terry, who died by suicide. Her body was discovered on the couch. Terry also shot and killed their grandson, Dalton, whose body was found under a blanket in one of the home's bedrooms.

TMZ broke the story ... officers from the Muskogee Police Department in Oklahoma raced to the home June 26 after a female called to report someone with a gun.

Jimmie and his wife, Chandra, have yet to make a public statement about the tragic incident ... but Jimmie was scheduled to race in a NASCAR Cup event in Chicago just days later. He withdrew from the event.

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