Police identified the man as Nikolai Lazukin, 27. His body was found Tuesday in a car 80 miles south of a burned house in Salem where his wife and three children were found dead. Authorities said the wife and two of the children had been shot, and an infant asphyxiated.
Neither police nor Deputy State Medical Examiner Larry Lewman would officially call the death a suicide. Police released no other details of their investigation.
Firefighters who entered the burning home discovered the bodies of infant Sefi Lazukin, 1-year-old Zoe Lazukin, 3-year-old Angelica Lazukin and the children's 26-year-old mother, Natalya Lazukin.
More than 100 people gathered for a memorial service outside the home Wednesday night, the Oregonian reported.
A youth group from the Slavic Christian Church in Salem, where the family worshipped, tied balloons to a fence, and the crowd sang "Amazing Grace" in Russian.
"They were all wonderful," said Irina Thompson, a relative of Nikolai Lazukin by marriage. "Nick was so good with the kids. I can't understand why this would happen, but sometimes people change."
Family members have spelled the father's name Nikolay. Police Lt. Dave Okada said police have seen the name spelled both ways but are spelling it Nikolai in their records.