A 17-year-old student from Wisconsin has been charged in connection with the deaths of his mother and stepfather, whose bodies were discovered in a severely decomposed state in February.

Nikita Casap, 17, had reportedly maintained perfect school attendance until the double homicide but now faces a lifetime behind bars.

The teen is charged with two counts of first-degree intentional homicide, two counts of hiding a corpse, theft of movable property, theft involving special circumstances, unauthorized use of a vehicle and two counts of identity theft for financial gain, according to court records.

Prosecutors allege the teenager shot and killed mom Tatiana Casap and stepdad Donald Mayer on February 11 before fleeing the scene and leaving their bodies to decompose inside their home.

The couple were discovered on February 28 during a welfare check, court documents reveal.

Casap's mother was found in an advanced state of decomposition, with her body described as 'blackened' and dried blood around her, while Mayer's body was discovered in another room, having suffered a gunshot wound to the back of his head.

Authorities say the teenager had previously confided in a female classmate about 'fantasizing' not only about killing his parents but also about taking his own life.

Disturbing surveillance footage from the crime scene reportedly shows a camera focused on the body of the stepfather, which had been covered with blankets and pillows.