The body of a missing 10-year-old Indiana girl was found inside a shed — and her stepmother has been arrested on murder charges, authorities said.

Skylea Carmack was discovered in a trash bag around 3 a.m. Wednesday behind her Gas City home, from which she supposedly vanished four days earlier, ABC News reported.

Police believe Skylea was already dead when her stepmother, Amanda Carmack, reported her missing Saturday night from the home. Her father, Kevin Carmack, told police his daughter might have run away because she was grounded, news station Fox59 reported.

Authorities said a “conglomerate of evidence” led them to arrest her 34-year-old stepmother — but no motive has been released for the killing.

The stepmother faces charges including murder, strangulation and neglect of a dependent resulting in death.

“To try to rationalize why someone would kill a 10-year-old, there’s no rationale for that,” Indiana State Police Sgt. Tony Slocum said Wednesday at a press conference. “That’s just an act of cowardice.”