A nurse returning from work discovered an intruder armed with a hammer in her home and strangled him with her bare hands, police said.
Susan Kuhnhausen, 51, then ran to a neighbor's house Wednesday night to report the intruder, identified as Edward Dalton Haffey, 59.
Homicide detectives said they have determined it was self-defense. They said a prosecutor is investigating but that they do not expect the case to go to a grand jury.
Police say there was no obvious sign of forced entry at the house when Kuhnhausen, an emergency room nurse at Providence Portland Medical Center, got home from work shortly after 6 p.m.
Haffey, a convicted felon with a long police record, was dead when police arrived.
"Everyone that I've talked to says 'Hurray for Susan,' said neighbor Annie Warnock, who called 911.
Under Oregon law people can use reasonable deadly force when defending themselves against an intruder or burglar in their homes.
"You didn't need to calm her," Warnock said. "She's an emergency room nurse. She's used to dealing with crisis."
Kuhnhausen was treated and released for minor injuries at Providence.
Haffey, about 5-foot-9 and 180 pounds, had convictions including conspiracy to commit aggravated murder, robbery, drug charges and possession of burglary tools.
Neighbors said Kuhnhausen's size — 5-foot-7 and 260 pounds — may have given her an advantage.