At the time of Williamson's disappearance, Ernie was separated from his wife Angie and lived across the street just to remain close with his children, and he happened to be staying over when he found out his daughter went missing.

The authorities, including local police, St. Louis County deputy sheriffs and FBI agents, conducted the search for the missing girl, and many members of the community volunteered to look for Williamson.

[2][3] Subsequently, the police received information from witnesses that they saw the girl being carried away by a man, who was identified as 24-year-old Johnny Allen Johnson (alias Movant), who was a friend of the Williamson family.

An autopsy revealed that Williamson died from blunt force injuries to her head, which caused skull fractures and bruising of her scalp and brain.

Furthermore, there were other injuries to the arms, shoulders, legs, and back, and signs of semen were found on the shorts of Johnson, which indicated that he had likely sexually assaulted the girl.

Based on further investigations, Johnson, who was previously convicted of burglary before the murder, was found to have abducted the girl and took her to an abandoned glass factory, where he attempted to rape Williamson.

Mourners, including Williamson's friends and members of the public, gathered at Twin Oaks Presbyterian Church to pay respects, and the memorial was broadcast live on television.

Standing trial before a St. Louis County jury, Johnson never denied that he murdered Williamson, but his main defence was diminished responsibility.

[18][19] As a final resort to escape the death penalty, Johnson filed last minute appeals to challenge his execution, stating that he was incompetent to be executed due to his schizophrenia, and his lawyers urged the courts to consider that it had affected his state of mind when the murder of Williamson happened, and added that he experienced delusions about the devil using his death to bring about the end of the world.

[31][32] On August 1, 2023, 45-year-old Johnny Allen Johnson was put to death via lethal injection at Eastern Reception, Diagnostic and Correctional Center in Bonne Terre.

[33] Prior to his execution, Johnson reportedly ordered a final meal of one bacon cheeseburger, curly fries and a strawberry shake.

[37] In memory of Williamson, her bereaved loved ones established a scholarship, and an annual community safety fair in her name, and provided child identification kits in these events.

Another relative revealed that Williamson's grandfather similarly turned to alcoholism due to his grief of losing a granddaughter and died.