Police in Baton Rouge, Louisiana, are investigating the death of local museum leader Sadie Roberts-Joseph after her body was discovered in the trunk of a car on Friday afternoon. A veteran activist, Roberts-Joseph founded the Odell S. Williams Now & Then Museum of African American History, now known as the Baton Rouge African American History Museum, in 2001.

Baton Rouge Mayor Sharon Weston Broome and state representative C. Denise Marcelle have both stated on social media that they believe the 75-year-old was murdered, but investigators have yet to declare an official cause of death. Roberts-Joseph was found in a car three miles from her home, according to reports.

The city’s police described Roberts-Joseph as “a treasure to our community” on Facebook, writing that “our detectives are working diligently to bring the person or persons responsible for this heinous act to justice.”

An autopsy is scheduled to be conducted today, and Broome is offering a $5,000 reward for information that leads to the arrest of anyone connected to Roberts-Joseph’s death.

The African American History Museum, located at the New St. Luke Baptist Church (where her brother is pastor), features exhibitions on African art, black inventors, and the Baton Rogue Bus Boycotts of 1953. It houses an authentic city bus from that period, as well as a garden that grows three varieties of cotton.

Each year, the museum hosts the city’s Juneteenth festival, organized by Roberts-Joseph, to mark the end of slavery in the US. She also helped found the Community Against Drugs and Violence program with the Baton Rouge police.

Exterior view of the Baton Rouge African American Museum. Photo by Blair via Wikimedia Commons.

The NAACP’s Baton Rouge Branch called Roberts-Joseph a “cultural legend” on Facebook: “From reviving Juneteenth [celebrations], to the culture preserved at her museum, she was a trendsetter and icon in this city.” She has been described as one of the last black oral street historians of Baton Rouge.

“We have to be educated about our history and other people’s history,” Roberts-Joseph told the local paper, the Advocate, in 2016. “Across racial lines, the community can help to build a better Baton Rouge, a better state, and a better nation.”

On Friday, Roberts-Joseph had visited her sister and neighbor, Beatrice Johnson, to bake a loaf of cornbread while her own oven was broken. “The bread is still there,” Johnson told the Advocate. “She never came back to get it.”

UPDATE, 5 p.m.: Roberts-Joseph’s body was found following a call to the police by an anonymous tipster, according to the New York Times. The report from East Baton Rouge Parish coroner William Clark ruled the death a homicide, listing the preliminary cause of death as “traumatic asphyxia, including suffocation.”