Kim Kardashian West said her "heart and prayers" are with an Alabama death row inmate who was executed despite a high-profile campaign to save his life.
The reality TV star, who is training to be a lawyer and is campaigning for criminal justice reform, championed the case of Nathaniel Woods.
Woods, 44, was convicted in 2005 for his role in the fatal shootings of three police officers in Birmingham, Alabama.
His co-defendant, Kerry Spencer, admits to pulling the trigger and denied Woods was involved, urging officials to halt the execution.
However, a last-minute bid to save Woods failed and on Thursday he died following a lethal injection, according to the Associated Press.
Shortly before news of his death was confirmed, Kardashian West warned an innocent man had been sentenced to die.
She said: "The court has lifted the temporary stay of execution for #NathanielWoods. The governor will NOT save his life. My heart and prayers are with Nate and his family.
"This is a tragic example of injustice in the system – in a few minutes Nate may die for a crime he did not commit.
"Nate will die for a crime another man confessed to and says Nate had nothing to do with. My heart and prayers are with Nate and his family and all the advocates who worked tirelessly to save his life."
Kardashian West later tweeted "RIP Nathaniel Woods".
She had been joined in the campaign to spare Woods the death penalty by Martin Luther King III, the son of the famed civil rights leader.
Activists raised questions around the original trial, alleging the defendant was given inadequate legal advice.
Earlier this week Kardashian West, 39, visited the White House with three women who had their sentences commuted by US President Donald Trump, allowing them early release from prison.
The mother-of-four said she and the women – non-violent offenders serving long sentences – planned to "discuss more change that our justice system desperately needs".
The freed women had their cases championed by grandmother Alice Johnson, who was released from prison in June 2018 following a campaign by Kardashian West.