By Dana Kozlov

Chicago (CBS) — Sandra Bland, the Naperville woman who died in a Texas jail in 2015, is the subject of a new documentary. Bland was found hanged after a controversial traffic stop and arrest. Bland’s mother and sisters were all featured in the film, hoping it helps to bring about change.

“It’s bittersweet,” Bland’s sister, Shante Needham, said.

And, for this oldest sibling, it’s still painful to relive Bland’s 2015 death and the questions that linger.

“To be honest with you, I don’t think I will ever have peace because I still don’t know what happened to my sister,” Needham said.

“Say Her Name”, being shown at Chicago’s Music Box Theatre, gives the audience a glimpse into Bland’s life, activism and spirit.

It also tries to unravel what happened between the time the 28-year-old was arrested during a Texas traffic stop and her death three days later in a Waller County jail cell, ruled a suicide by asphyxiation.

“If it were true, then I think that we should have been able to see the evidence proving that that was their truth,” Needham said.

Above all, Needham hopes this film makes people think about how police interact with civilians, especially civilians of color.

“I just hope people leave feeling inspired after watching this documentary to activate what’s already in them to make a change,” Needham said.

Needham said she still cries everyday, but she’s picked up her sister’s activism torch and said she continues to meet with families who have experienced police brutality and violence in their lives.

The officer who arrested Bland was ultimately fired, and Bland’s family was awarded almost $2 million from a wrongful death lawsuit that came with guarantees of procedural changes.

“Say Her Name” will be shown on Sunday and Tuesday with a question and answer segment after Tuesday’s screening.

The documentary airs on HBO on Dec. 3 at 9 p.m.