Detectives in a small western North Carolina town worked around-the-clock for days to identify the mysterious man spotted lurking outside the home of four family members found slain inside.

They eventually honed in on a man they described as a suspected opium trafficker from Wisconsin. And just seven minutes after their national alert went live with his license plate, authorities in Utah spotted his car on a highway headed for California.

The high-speed chase ended moments later with the suspect's green BMW in flames and his girlfriend — whom authorities say was his accomplice — shot to death beside him in an apparent murder-suicide.

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And so for now, the odyssey that began last Thursday half a continent away with the shooting and stabbing deaths of Lisa Saephan and her three children — 20-year-old Melanie, 18-year-old Pauline and 4-year-old Cody — remains a mystery.

"It's like trying to put together a big puzzle," Coy Reid, chief deputy with the Catawba County Sheriff's Office, said Wednesday. "They could've finished the rest of the pieces. We still have a lot to tie up and finish in the investigation."

Authorities said that investigation could ultimately end with Saephan's husband facing charges of trafficking drugs. Although he is not implicated in the deaths of his wife and three children, detectives suggest that Brian Tzeo's involvement in a drug trafficking ring with the suspects may have been behind the attacks.

"The information we have suggests the father was a drug distributor," Reid said. "He has cooperated with us. And we're not at liberty to talk about that right now. It's an ongoing investigation."

Tzeo hung up Wednesday when reached by phone.

Authorities named the suspect in the four slayings as Chiew Chan Saevang, 37. They said he killed himself and his girlfriend, Yer Yang, 40, of Long View after sheriff's deputies in Utah spotted them late Tuesday night and gave chase. After hitting another car, authorities, say, the BMW drove up an embankment, stopped on a hillside and caught fire.

Deputies who pulled the pair from the wreckage found them dead. Investigators there said they believe Saevang fatally shot Yang, then turned the gun on himself.

Detectives in North Carolina learned of the deaths as they prepared arrest warrants for Saevang for murder and for Yang for accessory after the fact to murder. Reid said days of poring over notes and taking in tips, including those generated by the case's appearance on "America's Most Wanted," lead them to Saevang and Yang. Both were also expected to have been charged with conspiracy to sell opium.

Authorities said Wednesday that Brian Tzeo would receive opium through the mail from Thailand, convert it to heroin and give it to Yang. She would take the heroin to Saevang in Wisconsin, where he would sell it, they said.

"There was some drug distribution that came out of that house," SBI spokesman Dave Call said Wednesday.

Investigators would not discuss details Wednesday about what happened on March 12 that possibly led Saevang to kill Tzeo's wife and the couple's three children at their home near Conover, about 40 miles northwest of Charlotte. Investigators have said Tzeo was at work when his family was killed. His youngest son Cody was found shot to death at the kitchen table, his fingers still inside his cereal bowl.

Funeral services were held Wednesday afternoon for the victims in nearby Newton. Tzeo has said he wants to take his family back to California for burial, but authorities have not said whether they would allow him to leave the state for that purpose.

Authorities found the victims after a friend of Pauline's called 911 on 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 after the friend said she had seen a suspicious man outside the house.

Tzeo has said he and his wife had separated and that he had an affair but they were still living together and trying to work things out.

Yang's criminal history showed convictions for forgery and larceny and several charged related to obtaining property by false pretense. Saevang faced several charges of trafficking in opium in Catawba County over the last six years.