(NewsNation) — “It was the first time he ever dropped his mask and became BTK in front of me,” Kerri Rawson, the daughter of serial killer Dennis Rader, said in an exclusive NewsNation interview about meeting her dad face-to-face for the first time in 18 years.

In 2005, Rader, also known as BTK, which stands for “bind, torture and kill,” was convicted of killing 10 people from 1974 to 1991. Investigators are currently looking into missing persons cases possibly associated with Rader.

Rawson flew to Oklahoma in June to help investigators in Osage County. She said she visited her father in prison for three hours in June and July to try and get information from him. However, he’s been uncooperative.

She said it took her dad a minute to process who she was.

“He’s lost like seven inches, and he’s in a wheelchair. He’s pretty much rotting, like, to his core,” Rawson said.

Earlier this week, Oklahoma authorities recovered “items of interest” while searching a Kansas property that formerly belonged to Rader. The items will undergo a “thorough examination” to determine their potential relevance to ongoing investigations, police said in a news release Wednesday.

According to Rawson, her dad “wants to live his life out at the prison that he’s at. … That’s one pressing point. If he’s not going to cooperate, then we’re going to do this the legit hard way, and he’s going to wake up some morning somewhere he doesn’t want to be.”