One of the country’s most famous missing person cases came to a sudden resolution earlier this year when the Georgia Bureau of Investigation announced an arrest in the death of Tara Grinstead.

Grinstead, a teacher and successful beauty pageant contestant, had been missing from her Ocilla, Georgia, home since October 2005. She was 30 when she vanished without a trace.

In late February, Ryan Alexander Duke was arrested with Grinstead’s murder. At the time, Crime Online‘s Nancy Grace said in an appearance on Good Morning America that she believed there had to be more involved in the sudden arrest, as Duke had not previously been a person of interest in the case.

Indeed, the following week, police arrested a second suspect in connection with Grinstead’s murder: Bo Dukes, who, like Duke, attended the high school where Grinstead worked as a teacher. The men, who are not related, had both graduated before Grinstead’s murder. Dukes who is accused of helping Duke hide Grinstead’s body, is believed to have led police to the murder suspect.

And this week, the woman who convinced Dukes to come forward has broken her own silence.

In a CBS This Morning clip from her upcoming appearance on 48 Hours, Brooke Sheridan said that she is the person who turned Dukes — her boyfriend — in, after he confessed that he was involved in Tara’s death and that Duke murdered her.

“I felt like I was gonna be sick. I didn’t know who I was staring at. I didn’t know who he was,” Sheridan said.

The woman claims she tried to convince Duke to turn himself in, but that he told her only wanted Grinstead’s family to know what happened to her — not the police.

So Sheridan contacted police herself.

“And I knew that he would probably serve the rest of his life in jail,” Sheridan said. “That family’s peace to me was more important than his freedom.”

Despite the confession, Sheridan says she still doesn’t understand why Duke killed the beauty queen.

“He said, ‘That’s something that only God and Ryan know,'” Duke reportedly told her.