A Chicago woman was found dead in a Texas jail cell this week after being arrested for allegedly assaulting a police officer. Friends and relatives of Sandra Bland told news channel ABC 7 they do not believe the county sheriff’s account of what happened, and #BlackLivesMatter activists on social media are taking up her cause—including a planned Friday protest at the sheriff’s office in Hempstead, Texas.

Bland, 28, was driving from Illinois to Texas to start a new job at her alma mater, Texas Prairie View A&M, when she was pulled over for improperly signaling a lane change on Friday, July 10, according to the Waller county sheriff’s department. She allegedly got into an altercation with the police officer who pulled her over and was taken into custody. A video taken by a bystander shows two policemen holding Bland down as she complains of their rough treatment:

Bland was found dead the morning of July 13 in her cell after spending three days awaiting a bond hearing. The sheriff’s department said the cause was “self-inflicted asphyxiation.” Sheriff Glenn Smith told ABC 7 that jailers saw Bland at 7 am for breakfast and heard from her at 8 am, and that she was found dead an hour later, despite their attempts to perform CPR.

An autopsy on Bland ruled that she died from suicide by hanging, a county forensic spokeswoman told the New York Daily News.

Bland’s friends and family are dubious that Bland—who was starting a new job and had recently spent the Fourth of July weekend with family in Chicago—would harm herself. Social media users are using the hashtags #WhatHappenedtoSandraBland, #SandraBland, #JusticeForSandy, and #BlackLivesMatter to express their skepticism over the official reports of Bland’s death and outrage at how she was treated.

Waller county district attorney Elton Mathis said that he has no information that would make him think that Bland’s death was anything other than a suicide. He did, however, tell the local news station that he found the circumstances bizarre.

“And that’s why it’s very, very important that a thorough investigation is done and that we get a good picture of what Miss Bland was going through the last four, five days of her life,” he said.

The investigation into Bland’s death has been turned over to the Texas State Rangers, the statewide law enforcement agency.