Police, Relatives at Odds Over Sandra Bland's Jail 'Suicide'

— -- Newly-emerged cell phone video shows the arrest of Sandra Bland, who died in custody Monday in Texas -- as the woman’s family and authorities disagree about the manner of her death.

Authorities said that Bland, 28, committed suicide, but her family isn’t buying it.

A prosecutor said Thursday that he will present the findings of a Texas Rangers' investigation to a grand jury. The FBI is also investigating the circumstances surrounding Bland's death.

Bland, who lived in the Chicago suburb of Naperville, graduated from Prairie View A&M University and was planning to move back to Texas.

She was arrested on July 10 in Prairie View following a routine traffic stop, with authorities alleging that she was “argumentative and uncooperative.”

In cell phone video of the arrest -- which was posted to YouTube -- Bland can be heard questioning officers’ tactics, accusing them of slamming her to the ground.

Bland was found dead in her cell three days later.

Waller County District Attorney Elton Mathis said an autopsy found Bland died by asphyxiation and that she used a plastic bag to hang herself from a partition in her cell. He added that although jail video didn't show what went on in Bland's cell, it showed no one went in or out of it from the time she was placed there until a jailer found her unconscious.

Bland previously discussed her struggle with depression in a video posted to Facebook in March.

"I want you guys to know it's a daily struggle. It's a daily test," she said. "Depression is nothing but the devil. It's a way of mind and it's a way of thinking."

However, her relatives say she was days away from starting a new job and would never take her own life.

“Based on the Sandy I knew, that’s unfathomable to me,” said Sharon Cooper, Bland’s sister.

The Associated Press contributed to this report.