Missouri Governor Mike Parson has announced that the state will proceed with the scheduled execution of Johnny Johnson, despite ongoing claims from Johnson's attorneys that he is mentally incompetent, according to ABC News.

Johnson, 45, is set to receive a lethal injection on Tuesday for the abduction and murder of 6-year-old Casey Williamson in Valley Park, Missouri, in July 2022.

Johnson's legal team has filed an appeal with the US Supreme Court seeking to halt the execution, and they have also requested clemency from Governor Parson, asking for a reduction of Johnson's sentence to life in prison.

They argue that Johnson's mental illness has left him unable to comprehend the connection between his actions and the impending execution.

Missouri Governor Mike Parson has denied the clemency request, pointing out that multiple courts, including the original trial judge and the 8th US Circuit Court of Appeals, have already rejected Johnson's claims of incompetency in the days leading up to the execution.

READ NEXT: Missouri Convict Becomes First Openly Transgender Woman Executed in US 

Johnny Johnson's Mercy Plea

Johnny Johnson's case has garnered widespread attention and calls for clemency due to his diagnosed schizophrenia and continued struggles with mental illness, The Kansas City Star reported.

According to his attorneys, Johnson has been hearing voices and has developed a belief that his impending execution is linked to apocalyptic visions involving Satan and the State of Missouri.

Several notable figures, including Democratic Reps. Emanuel Cleaver and Cori Bush have urged Missouri Governor Mike Parson to halt the execution.

They point to extensive evidence suggesting that Johnson lacks a rational understanding of the reasons for his execution, likely due to his mental health condition.

Adding to the voices calling for clemency, Archbishop Christophe Pierre, the Vatican's ambassador to the US, wrote a letter on behalf of Pope Francis, appealing for mercy based on the shared humanity of all individuals.

While recognizing the seriousness of Johnson's criminal conduct and its consequences, the letter emphasized the sacredness of life and the need to honor the gift of life even in challenging circumstances.

Casey Williamson's Brutal Death

Johnny Johnson's conviction stemmed from the tragic and heinous killing of 6-year-old Casey Williamson in Valley Park, Missouri, in July 2002.

The young girl's disappearance sparked a frantic search in the small suburb of St. Louis, per Yahoo! News.

Casey's mother had been childhood friends with Johnson's older sister, and they had even babysat him.

Johnson attended a barbecue the night before the killing and was allowed to stay overnight on a couch.

The following morning, Johnson lured Casey to an abandoned factory nearby. He carried her on his shoulders as they walked to the derelict site.

Tragically, Johnson attempted to sexually assault Casey, prompting her to scream and struggle.

He then brutally killed her with a brick and a large rock and later washed off in the nearby Meramec River, according to court documents.

Johnson did not attempt to hide his actions and confessed to the crimes on the same day.

Despite search efforts by first responders and volunteers, Casey's body was found buried beneath rocks and debris in a pit less than a mile from her home.

READ MORE: Missouri Man Walks Free After 27 Years 

This article is owned by Latin Post.

Written by: Bert Hoover

WATCH: Execution of Johnny Johnson will proceed on Aug. 1, stay lifted - From FOX 2 St. Louis