"In an attempt to subdue Bill Currier, Keyes hit him with a shovel, but he continued to struggle and yell wanting to know where his wife was," Donovan said. When Keyes was unable to subdue Bill Currier, he shot him to death, the state attorney said.
"They fought to the end," a choked up Donovan said at the news conference.
Keyes then returned to Lorraine Currier and sexually assaulted her before strangling her. He put each of his victims in garbage bags, put them in the corner of the farmhouse and covered them in debris.
Keyes drove away with the intention of robbing a bank, but had some trouble with the Curriers' car, so he abandoned it and drove his rental car to Maine. Shortly after, he stopped at an national forest to burn the couple's property and then went back to Vermont to visit the crime scenes.
He disposed of the two guns and a silencer in a reservoir and began to make his way back to Alaska.
"By all accounts, [the Curriers] were friendly, peaceful, good people who encountered a force of pure evil acting at random," an investigator said at today's news conference. Authorities called the ongoing investigation a "huge case, national in scope."
Before his death, Keyes indicated that he also killed four people in Washington State and one person in New York, but did not give the victims' names, authorities said.
Keyes had been facing a March trial in Anchorage federal court--and possibly the death penalty--for the killing of Koenig.
Samantha Koenig was last seen Feb. 1 on surveillance video that showed her leaving the Common Grounds Espresso stand in Anchorage with an armed man. All of the coffee stand's cash was also missing.
Prosecutors said Keyes stole a debit card from a vehicle she shared that was parked near her home, obtained the personal identification number and scratched the number into the card, according to the AP.
After allegedly killing Koenig, Keyes used her phone to send text messages to conceal the abduction, according to prosecutors. He flew to Texas and returned Feb. 17 to Anchorage, where he sent another text message demanding ransom and directing it to the account connected to the stolen debit card, according to prosecutors.
Keyes was arrested in Lufkin, Texas, March 16 after he used Koenig's debit card. The FBI contends Keyes killed Koenig less than a day after she was kidnapped. Her body was recovered April 2 from an ice-covered lake north of Anchorage.
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, the Anchorage Daily News reported.
Authorities wouldn't say how Keyes killed himself, only that he was alone in his cell. An autopsy will be conducted.
Keyes owned a construction company in Anchorage. According to the website for Keyes Construction at the time of his arrest, Keyes worked in Washington State in the mid-1990s and then served three years in the Army infantry, stationed in Fort Lewis, Fort Hood, and Sinai, Egypt. According to the site, he then worked from 2001 to 2007 for the Makah Tribal Council in Neah Bay, Wash., before moving to Alaska.
Koenig had been working at the Common Grounds Espresso stand for about a month before her disappearance and, her father said, she was really enjoying it.
"She's a sweetheart. She's got the biggest heart and she has genuine love and care for people. She befriends people so easily," James Koenig told ABC News in March. "Everyone that meets her, they call her their best friend. That's just her personality. She's funny and she loves life."
Alaskan officials are expected to release a timeline of Keyes' U.S. travels later today.