MUSKOGEE, Oklahoma - A Muskogee man pleaded guilty Thursday to killing his wife and encasing her body in concrete inside of a manhole behind the home of his mother in 1999.

Jeff Grannon, 57, was charged with first degree murder in the death of Carol Grannon following his arrest in February 2011.

Carol Grannon was 28 years old and the mother of four children, the youngest being only 8, when she disappeared in 1999.

Carol's children were in the courtroom as Jeff Grannon confessed. They heard all the horrific details of how their mother was killed, but one question was never answered.

"Surreal because all of these years, you know, prayed and prayed and prayed," said Laura Walker, a friend.

Jeff Grannon admitted in court Thursday to strangling his wife, Carol with a zip-tie, then encasing her body in concrete inside a manhole near his mother's home in 1999.

Sheriff's Investigator Eddie Walker is Carol's ex-husband and father of two of her four children.

"It was an emotional day, especially for the children, because it was the first time they actually had to sit in the same room with Jeff Grannon," said Eddie Walker.

Jeff Grannon's son led investigators to the manhole after he was arrested in a drug sting last February. He told authorities his father killed Carol and hid the evidence.

Jeff Grannon relayed the same story in court -- in front of Carol's sons and daughters.

"He told one of the girls one time that he'd been to prison before and he wasn't scared of it, and she told him, ‘Well, I guess you're going back home then,'" Walker said.

Before the tip that led to her body, police and deputies never stopped searching for Carol. Walker says he suspected Grannon the entire time and confronted him 10 years ago.

"I looked at him in his eyes and I told him, ‘I think you did this, and I almost know you did this, and one day I'll find out," said Eddie Walker, the victim's ex-husband an investigator with the Sheriff's Office.

"And he said, ‘Well, whatever you think.'"

Now, Carol's family finally knows what happened to her all these years later.

"The only thing I think the kids regret was, they didn't get it out of him why he did it," Walker said.

They may never know Grannon's motive.

Jeff Grannon was sentenced to life in prison with parole. It's still unclear if prosecutors plan to file charges against his son, who was a juvenile when he helped bury Carol's body.