A sex offender who owed rent to Sadie Roberts-Joseph — the 75-year-old founder of Baton Rouge’s African American history museum, who was found dead in the trunk of her car — has been arrested for her murder, according to new reports.

Ronn Jermaine Bell, who lived in one of the Louisiana activist’s rental homes and owed her $1,200 in unpaid rent, was busted on first-degree murder charges, NBC News reports.

Bell, 38, pleaded guilty to sexual battery of an 8-year-old girl in 2007 ahead of an aggravated rape trial, and served seven years behind bars, WAFB News reports. He was in jail for failing to register as a sex offender when he was charged Tuesday, the outlet said.

Authorities say they’re still investigating the motive in the murder, but it isn’t being considered a hate crime or tied to Roberts-Joseph’s community activism.

She was found Friday afternoon in her car about 3 miles from her home, and the city’s coroner determined Monday that she died of suffocation.

Bell has allegedly admitted to being in the area when the car was left there, and his DNA was found on her remains, WAFB reported.

She founded the museum in 2001 and also organized its annual Juneteenth festival, marking the date on June 19, 1865, when the abolition of slavery was announced in the state of Texas.

“I’m heartbroken that our community has lost such a kind and selfless soul in such a violent, tragic manner,” East Baton Rouge Sheriff Sid Gautreaux said, according Baton Rouge paper The Advocate.

“I have known and loved Mrs. Sadie Roberts-Joseph for years and admire and respect her dedication to education and our community. I’m grateful for the swift action of the Baton Rouge Police Department and Louisiana State Police in finding her alleged killer and putting him behind bars.”