A 14-year-old Florida girl accused of killing her newborn baby and hiding the body in a shoebox will be prosecuted as an adult, the Polk County State Attorney's Office confirmed Friday.

A grand jury indicted Cassidy Goodson Thursday on charges of first-degree murder and aggravated child abuse.

An arrest affidavit stated that Goodson told police she gave birth to her child alone in her bathroom on September 19, at one point using scissors to "'pry' the child out." She then allegedly choked the baby for approximately one minute until he stopped breathing, the arrest affidavit said.

According to the affidavit, Goodson told her mother she had suffered a miscarriage and flushed the fetus down the toilet. Goodson's mother told police that while she was collecting laundry four days later, on September 22, she found the body in a shoebox hidden amid dirty clothing in the teen's bedroom, the affidavit stated.

If convicted of murder, Goodson could face life in prison. She was expected to appear in court Friday.

Goodson's mother and grandmother reportedly told The Ledger Wednesday that they did not believe the teen knew she was pregnant before giving birth.

Grandmother Donna Goodson said the girl told her, "If I knew I was pregnant, it would have been different," according to the paper.

According to court documents, authorities believe Cassidy Goodson did know she was pregnant and tried to hide it by wearing "baggy, loose clothing."

When contacted by HLN earlier this week, Goodson's mother declined to comment on the case.

Police said in the arrest affidavit that Goodson told them she killed the baby because "she was afraid her relationship with her parents would change."

A public defender representing Goodson could not be reached for comment Friday.