Just days after the body of a prominent civil rights activist in Louisiana was found in the trunk of a car, police said they have arrested a man who knew her.

Ronn Jermaine Bell, 38, was arrested and charged with first-degree murder in the death of Sadie Roberts-Joseph, the Baton Rouge Police Department said at a press conference Tuesday.

Bell was a tenant in one of Roberts-Joseph's homes, and he was behind on rent by about $1,200, police said.

Police also said Bell is a registered sex offender and had served time in prison for the sexual assault of a young girl.

Authorities said they still do not know the motive for Roberts-Joseph's killing.

Roberts-Joseph, 75, was a well-known community leader who worked with law enforcement on programs tackling drug use and gang violence. She was the found and curator of Baton Rouge's African-American museum and had recently organized its annual Juneteenth festival celebrating the date of June 19, 1865, when those enslaved in Texas were finally freed.

Roberts-Joseph was last seen Friday at her sister's house, from whom she lived three doors down.

Her body was found about 3 miles from her home just a few hours after she had been last seen. Her cause of death was "traumatic asphyxia, including suffocation," according to a statement from the coroner's office.

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