Authorities initially thought medical issues caused the March 10 death of a 61-year-old man at his home in Portland.
But an autopsy by the Oregon state medical examiner's office determined that Eugene Bigboy had been killed.
Police say homicide detectives arrested his nephew, 22-year-old Matthew Galen Bigboy, on Sunday in connection with the death. He was booked into the Multnomah County Jail on a murder charge.
It's the sixth homicide this year in Portland.