Baton Rouge mourns after beloved activist Sadie Roberts-Joseph found dead in trunk of a car

The city of Baton Rouge is mourning the death of a beloved activist and founder of the city's only African-American history museum.

An autopsy conducted by the East Baton Rouge Parish Coroner's Office determined that 75-year-old Sadie Roberts-Joseph's death was a homicide resulting from "traumatic asphyxia, including suffocation." Traumatic asphyxia is caused by "a severe crush injury causing sudden compression of the thorax" or chest, according to the International Journal of Emergency Medicine.

"It is with great sadness and respect we investigate any unexpected or traumatic death," the coroner's office said in a release. "When our investigation involves an innocent victim, such as Ms. Sadie Joseph, it is particularly tragic. Our condolences are extended to Ms. Joseph’s family and friends."

Roberts-Joseph was last seen visiting her sister at 11 a.m. Friday. She was found dead in the trunk of a car at 3:45 p.m. about 3 miles from her home, the Advocate reported.

"Friday, she came by (because) she had mixed some cornbread, but her oven went out, and she brought it here to put in the oven," Beatrice Johnson, one of Roberts-Joseph's 11 siblings, told the Advocate. "The bread is still there."

Baton Rouge police say they are "working diligently to bring the person or persons responsible for this heinous act to justice."

"The Baton Rouge Police Department joins the community in mourning the loss of Ms. Sadie Roberts-Joseph. Ms. Sadie was a tireless advocate of peace in the community. We had opportunities to work with her on so many levels," the Baton Rouge Police Department said in a statement. "Ms. Sadie is a treasure to our community, she will be missed by BRPD and her loss will be felt in the community she served."

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Roberts-Johnson founded the Odell S. Williams Now & Then Museum of African-American History in 2001.The museum features African art, exhibits on growing cotton and black inventors, as well as a 1953 bus from the period of civil rights boycotts in Baton Rouge. It also has prominent exhibits on President Barack Obama, whose presidency Roberts-Joseph cited as an inspiration to children.

She also organized an annual Juneteenth festival at the museum, marking when Maj. Gen. Gordon Granger came to Galveston, Texas, to inform its residents that President Abraham Lincoln two years earlier had freed the slaves, and to pressure locals to comply with Lincoln's directive.

Baton-Rouge Mayor-President Sharon Weston Broome called the museum "a testament of her visionary and pioneering leadership."

"She loved this city and its people," Broome said in a statement. "Her commitment to the cultural and educational fabric of our community is beyond description."

Broome noted that cash rewards up to $5,000 are offered for information that leads to the arrest and indictment of the person or persons who committed a felony. Tips can be submitted to Greater Baton Rouge Crime Stoppers, a privately owned, non-profit anonymous tip hotline .

State Rep. C. Denise Marcelle also urged anyone with information about Roberts-Joseph's death to contact authorities.

"My heart is empty," Marcelle said in a Facebook post. "This woman was amazing and loved her history. She never bothered anyone, just wanted to expand her African American Museum downtown, where she continually hosted the Juneteenth Celebration yearly. I loved working with her and am saddened by her death."

Contributing: The Associated Press

Follow N'dea Yancey-Bragg on Twitter: @NdeaYanceyBragg

This article originally appeared on USA TODAY: African-American history museum founder found dead in trunk of car