Cyntoia Brown, whose life sentence for killing a man when she was 16 inspired a documentary and celebrity support, walked free from prison in Tennessee on Wednesday after 15 years behind bars.

"Early this morning, offender Cyntoia Denise Brown was released from the Tennessee Prison for Women," the Tennessee Department of Correction said in a statement issued at 3:26 a.m. (4:26 a.m. ET).

Now 31, she was convicted as a teen of murdering a man she said had hired her for sex.

Her story led celebrities such as singer Rihanna, actress Alyssa Milano and reality television star Kim Kardashian West to advocate on her behalf and is cited as an example of the need for criminal justice reform.

She said she shot a man because she feared for her life

Brown was 16 when she shot and killed Johnny Mitchell Allen, 43, in 2004 after he allegedly paid her for sex. She said that she shot Allen, of Nashville, when she saw him reaching for what she believed was a gun while they were in bed at his home.

Prosecutors have argued that the motive was not self-defense as she claimed, but robbery.

At the time of the crime, Brown was a runaway and living with her 24-year-old boyfriend, a pimp known as "Kut Throat," who she said raped her and forced her into prostitution.

The teenage Brown was tried as an adult and convicted of first-degree murder, first-degree felony murder, and aggravated robbery. Two years after the crime, she was sentenced to life in prison.

Under Tennessee law, Brown would not have been eligible for parole until she served at least 51 years behind bars.

Celebrity support brings national attention

Kardashian West, who has recently advocated successfully for the release of other prisoners, was one of the first celebrities to publicly call for Brown's release. She wrote on Twitter in November 2017 that she asked her attorneys if they could help Brown.

Other stars followed suit, including rapper Meek Mill, NBA legend LeBron James, comedian Amy Schumer, rapper Drake and Rihanna, who wrote in a November 2017 Instagram post that "something was horribly wrong" with the justice system.

Demand that Gov. @BillHaslam grant Clemency for Cyntoia Brown NOW! https://t.co/GMk9ZtZ5ZU — Alyssa Milano (@Alyssa_Milano) December 30, 2018

In December 2018, Schumer and Milano tweeted at then-Tennessee Gov. Bill Haslam asking that he grant clemency for Brown. "She deserves our empathy and your mercy," Schumer wrote.

Brown's story also inspired a documentary in 2011 called "Me Facing Life: Cyntoia's Story," about her life behind bars. In July, Netflix announced that it had acquired a documentary on Brown that will "give additional insight on her years in prison and the path to her newfound fate," according to a press release.

A chance at freedom

In January, Brown won a major victory when Haslam granted her full commutation to parole. She will remain on parole for 10 years.

Haslam did not mention the high-profile support Brown received in his explanation for granting her clemency. Instead, he praised Brown for the "extraordinary steps" she took while in prison "to rebuild her life."

Inmate Cyntoia Brown of the Tennessee Prison for Women delivers a commencement address before receiving her associate degree from Lipscomb University, Dec. 18, 2015. Ricky Rogers / AP file

During her time behind bars, Brown earned a GED and an associate degree with a 4.0 GPA, Haslam said in his statement. She also served as a mentor and advocate for women in prison and earned a bachelor's degree in May, according to The Tennessean.

"Transformation should be accompanied by hope," Haslam said in his January statement.

Brown, in a statement her attorneys released after she was granted clemency, thanked Haslam and her supporters and vowed to spend the rest of her life helping others.

"My hope is to help other young girls avoid ending up where I have been," she said.