Saevang was wanted in last week's killings of Lisa Saephan and her three children - 20-year-old Melanie, 18-year-old Pauline and 4-year-old Cody - at their home outside of Conover.
Detectives said earlier this week that the four were shot and stabbed to death.
Saevang's vehicle was spotted in Utah after authorities in North Carolina became aware he may have been in the state headed toward California. Washington County sheriff's deputies tried to stop the vehicle around 11:20 p.m., and the vehicle hit another car, then drove up an embankment and came to a rest on the hillside.
While deputies were approaching, the vehicle caught fire. They pulled Saevang and a woman from the vehicle, then determined they were already dead.
Search warrants for the victim's home in Conover released Tuesday showed investigators took a knife, pistol and three computers from inside. They also found cell phones and a clear plastic bag of a "suspected controlled substance."
Officials have said Saephan's husband and the children's father, Brian Tzeo, was at work when his family was killed. But, detectives say he knew Saevang - a reported opium smuggler - and could face drug trafficking charges.
Investigators believe Saevang entered the home through an unlocked back door. Having an unlocked door in the community, tucked among rolling hills and farmland, wasn't uncommon in the family's subdivision, investigators said.
Investigators found the family after daughter Pauline's friend called 911 last Thursday morning, screaming and sobbing as she told the operator Pauline had just been pulled into her home and stabbed by a man.
The friend had picked up Pauline for school that morning, but they went back to the house after the friend she had seen a suspicious man outside the house.
Her young brother was shot at the kitchen table, and her sister was killed after she called Pauline and told her not to return to the house. The mother also was found dead inside.
Funeral services for Saephan and the children are scheduled at a funeral home in nearby Newton.