Police in Louisiana are investigating the presumed slaying of a prominent civil rights activist and founder of an African-American history museum whose body was found in the trunk of her car in the state capital, Baton Rouge, officials said on Sunday.

The remains of Sadie Roberts-Joseph, 75, were discovered on Friday afternoon about 3 miles (4.8 km) from her home near the Southern University and A&M College campus, but the cause of her death was not immediately known, according to authorities.

Police were led to the victim by an anonymous caller who reported a body in the trunk of a vehicle, Baton Rouge Police Department Sergeant L’Jean Mckneely said by email.

Roberts-Joseph’s body was discovered as the city braced for the possibility of severe flooding from Tropical Storm Barry, which blew into southern Louisiana as a hurricane on Saturday.

Police declined to give any further details of the investigation, although a message posted by the department on its Facebook page made clear authorities were treating Roberts-Joseph’s death as a homicide.

“Our detectives are working diligently to bring the person or persons responsible for this heinous act to justice,” said the message. It hailed Roberts-Joseph as a “tireless advocate of peace in the community.”

An autopsy on Monday will determine the cause and manner of death, said Shane Evans, chief of investigations for the East Baton Rouge Parish Coroner’s Office. He said there was “no initial evidence” to suggest it was suicide or an accident.

In addition to founding the Baton Rouge African-American History Museum, which opened in 2001, Roberts-Joseph launched the nonprofit group Community Against Drugs and Violence.

According to The Advocate newspaper in Baton Rouge, she also organized the city’s annual Juneteenth festival commemorating the U.S. abolition of slavery by President Abraham Lincoln’s Emancipation Proclamation, which was belatedly announced in the state of Texas on June 19, 1865, after the end of the Civil War.

Although she never held public office, Roberts-Joseph ran unsuccessfully for the U.S. Senate in 1996 and for lieutenant governor of Louisiana in 1999, according to the newspaper.

One of her 11 siblings, Beatrice Johnson, told The Advocate she last saw her sister on Friday when Roberts-Joseph stopped by with some cornbread batter she had mixed and wanted to bake at her sister’s home because her own oven “went out.”

“The bread is still there,” Johnson was quoted as saying. “She never came back to get it.”