COLUMBIA, S.C. -- The man who kidnapped and killed a 15-year-old Columbia girl orchestrated almost every part of the crime, including a final attempt to frame someone else for the murder, according to documents reviewed by The Associated Press and an interview with the sheriff.

The investigation was exhaustive and included hundreds of pieces of evidence and dozens of interviews. But it wasn't until Freddie Grant's own daughter was charged as an accessory did he admit to killing Gabrielle Swainson, who was known as Gabbiee.

"This was not a crime of passion that just happened. This was a plan - stalking, sexual assault and murder," Richland County Sheriff Leon Lott said.

The AP reviewed several hundred pages in an investigative file after a Freedom of Information Act request and months of wrangling over what could be released because Grant is being investigated in the disappearance of a second woman. The file redacted many names and addresses, making it difficult to determine who made statements to investigators.

Gabbiee disappeared in August 2012. Investigators pored over woods near Grant's home when she first went missing, but they didn't find her because she was buried in a five-foot deep hole, according to sheriff's office reports. Grant, a landscaper, had carefully filled the hole and spread pine straw all around it. Deputies only found her after he led them to her body in June.

In the woods, Lott stood near Grant as he pointed out the spot. Grant offered no explanation or apology for the killing. The documents showed Grant was unhelpful and defiant throughout the investigation.

"I pray for the safe return of Gabrielle. I had nothing to do with it and I will not answer any questions," Grant was quoted as saying in one report.

Grant pleaded guilty to murder in August and accepted a 30-year sentence.

"We had to make a deal with the devil, because we wanted to bring home Gabbiee," Lott said.

The deal came about because Grant ordered his own daughter to try to plant Swainson's cellphone to frame some of the people searching for the teen, who looked for her in Myrtle Beach days after she disappeared, but his plan backfired when deputies tracked Grant's 27-year-old daughter through her cellphone and debit card to the area at the time the phone was found.

Gabbiee was Grant's girlfriend's daughter. On the day she disappeared, co-workers told investigators Grant left work early. There were four hours between the time the teen's mom left for work and Grant showed up at her house because she had discovered the teen was gone, and Lott thinks Grant kidnapped the teen, sexually assaulted her and killed her during this time, waiting to bury her until the next day.

Reports from the crime lab retrace the harrowing steps of the crime. Blood in Gabbiee's bed indicated she was likely taken by force. Cellphone records showed Grant was at the teen's home when she was by herself, and the last signal from Gabbiee's phone came near Grant's house. The teen's DNA was on cups with alcohol in them at Grant's home, where Lott thinks she was forced to drink. Duct tape found at a junkyard near the killer's home had the impression of a mouth on them as if someone taped it shut along with DNA from both Swainson and Grant.

Once Gabbiee was reported missing, several people told investigators Grant behaved strangely when he came to her home. Grant said he found a note from the teen that said she was running away because she was gay, but Lott said the handwriting did not match the teen's.

One person said Gabbiee talked about receiving text messages from Grant saying she was beautiful and he could help her since she wasn't "experienced in the area of sex." Grant dismissed the messages, saying he was trying to send them to the teen's mother and hit the wrong button.

Deputies eventually arrested Grant, charged him with kidnapping and kept pressing him to talk. He refused. A search of Grant's home found ammunition the convicted felon wasn't allowed to have and he was convicted and sentenced to more than 17 years.

After his sentencing, a federal marshal heard Grant say: "Oh man, that was more time than I expected, but I've got away with enough (stuff) in my life. I guess it is time I do my time."

Prosecutors pressed forward with the kidnapping charge, and Lott thinks the pressure forced Grant to try to figure out a way out. The discovery of the cellphone and the arrest of his daughter likely left him little choice but to lead authorities to Swainson's body and take a plea deal.

"While he could kill someone else's daughter, he could save his own," Lott said.

The teen's cellphone was found outside a Myrtle Beach grocery store in June in good condition. A delivery driver found it, charged it and contacted Gabrielle's mother.

Investigators figured it couldn't have been outside for 10 months.

"We knew it had been stored somewhere, probably as a trophy because it had Gabbiee's picture on it," Lott said.

Deputies checked the cellphone and bank records for Grant's daughter, who was in the area around the time the phone was found. Investigators has been following Dominque Grant closely because she tried to help her father's defense on the federal ammunition charges, saying they were her bullets found in his home.