When Keyes realized that Koenig did not have her cell phone, he went back to the coffee stand to get it as it was an integral part of his plan. He used the phone to text Koenig's boyfriend and the owner of the coffee stand.
"The text messages made it appear that Samantha just had a bad day and was leaving town for the weekend," investigators said. "Keyes then took the battery out of Samantha's phone."
When he asked her for her debit card, she explained that it was in the truck she shared with her boyfriend at her house and gave him the pin number.
"Keyes put Samantha in the shed in front of his [Keyes'] house, bound her, and turned the radio up in the shed so no one would hear her if she screamed," the release said. "He also told her that he had a police scanner and would know if she attempted to alert the neighbors."
Keyes went to Koenig's house for the debit card and was confronted by Koenig's boyfriend who was looking for her. The boyfriend went into the house to call for help and Keyes was gone with the debit card by the time he got back.
Keyes returned to the shed, sexually assaulted Koenig and strangled her, the statement said.
"Keyes left her in the shed and then went back inside his house, where he packed for a pre-planned cruise that he was taking from New Orleans," authorities said.
He left Feb. 2 and returned Feb. 17. Upon his return, he used a typewriter to prepare a ransom note and demanded that $30,000 be deposited into the account tied to the debit card.
He went back to the shed and took steps to "make it appear that he was still alive" and took a Polaroid photo of her tied up. His arm was in the photo holding a newspaper from Feb. 13, the statement said.
He put the note in a park and texted its location to Koenig's boyfriend. Police recovered the note.
"In the days that followed, Keyes dismembered Samantha's body and drove out to Matanuska Lake, where he cut a hole in the ice and put her body in the lake," investigators said.
Koenig's father deposited donated reward money into the ransom account and Keyes was arrested after ATM withdrawals were made in Anchorage, Arizona, New Mexico and Texas.
The FBI has also released an ominous list of 35 trips Keyes made around the U.S., Mexico and Canada over the last eight years.
Keyes, the owner of an Anchorage construction company, had been facing a March trial in Anchorage federal court--and possibly the death penalty--for the killing of Koenig.
While in jail he had been confessing to at least seven other killings in Washington, New York and Vermont. Police have confirmed that he was responsible for the deaths of Bill and Lorraine Currier of Essex, Vt.
Investigators are now piecing together a deadly puzzle that is uncovering a macabre lifestyle of Keyes traveling to kill simply because he "liked to do it," prosecutors said.
Police and the FBI spent hours talking to Keyes in the months after his arrest and he was cooperating, talking to investigators as recently as Thursday.
Authorities wouldn't say how Keyes killed himself, only that he was alone in his cell. An autopsy will be conducted.
The FBI is asking for the public's assistance with any information about Keyes' travels in order to identify additional victims. They ask that anyone with information contact the FBI at 1-800-CALL-FBI.