The charging decision means if Richard Atkisson is convicted, the only possible sentences are the death penalty or life in prison without possibility of parole.
A sheriff's deputy found the bodies of the two victims, 20-year-old Michael Henderson and 66-year-old Joseph Moisa, Sunday morning while doing a routine sex offender address check at Moisa's Spanaway home.
A vehicle associated with the home was later found by Tacoma police officers near South 96th Street and Pacific Avenue South. Four people, including Atkisson, were initially detained for questioning. Atkisson was eventually arrested and the other three were released.
Prosecutors say Atkisson has since confessed to the murders, and told investigators Moisa and Henderson were grooming boys for sex. Atkisson said Moisa asked about bringing Atkisson's son to the home and that's what triggered the deadly assault, according to court documents.
Atkisson told detectives he first beat Moisa with a pipe, and when Henderson heard the commotion and came into the room, Atkisson forced Henderson to his knees and beat him to death, investigators said. Atkisson added that the when he noticed the pipe didn't kill Moisa, be placed a plastic bag over his head, prosecutors said.
"Though the defendant's motives are murky, the premeditation and brutality are clear," Prosecutor Mark Lindquist said in a statement announcing the charges.
Atkisson remains held without bail in a Pierce County Jail. Prosecutors say Atkisson had a felony warrant from Tulare County, Calif., for violating his supervision and failing to register as a sex offender there.
In 1993, Atkisson was sentenced to 23 years in prison for rape and also has prior convictions for burglary and failing to register as a sex offender, prosecutors said.
Atkisson remains held without bail in a Pierce County Jail.
Lindquist has 30 days to decide whether to seek the death penalty, although Governor Jay Inslee has currently imposed a moratorium on the use of the death penalty while he is in office.