Somkhith Soulinho, 31, killed his girlfriend and former sister in-law
Soupaphane Homsombath, 24, her 8-year-old son and 5-year-old daughter.
Soulinho then shot himself, police said.
Investigators say the triple murder and suicide was a domestic issue and
they are trying to pinpoint the motive.
Detective Paul Dolbey, a Portland Police Bureau spokesman said witnesses
reported they heard several shots fired inside the building at about
5:30 a.m. Thursday.
Dolbey said the landlord unlocked the door for police, who found the bodies.
"It's going to be quite a complicated scene, each one of the victims
represents a mini crime scene, if you will, and then you have the
overall apartment," Dolbey said.
The mother was shot dead on the couch. Her son, Lionel Homsombath, was
shot twice in the head as he lay in living room and her daughter, Leana
Homsombath, was stabbed to death in a bedroom. An autopsy will be performed.
Soulinho had a history of violence. In 1999, he shot his older brother,
Tia Soulinho, in the arm. He spent five years in prison for the crime.
He has also spent time in the Oregon State Hospital for mental health
issues.
Tia Soulinho, who lost his brother, children and ex-wife, said the crime
was hard to believe.
"I feel a lot of hurt. I feel a lot of pain," Soulinho told The
Oregonian newspaper. "But there's nothing I could do about it."
Tia Soulinho said he had a cordial relationship with his younger brother
but said most people were scared of him.
Family and friends believe drugs may have played a role in the crime.
At the scene, Chief Derrick Foxworth said some of his officers were
"pretty shook up. They're thinking about their own families. ... they
see their own kids lying there."