A "rage killing" may have taken place inside Lori and Mark Hacking's apartment hours before Lori was reported missing, FOX News has learned.

An investigative source working on the case told FOX News that 27-year-old Lori Hacking (search) was likely attacked inside the apartment, sometime between the night of Sunday July 18 and the morning of Monday July 19, when she was reported missing.

Police would not confirm the theory, saying Lori Hacking is still considered a missing person.

Sources close to the case said there was some evidence of a struggle, but no indication that it was a chaotic situation. Though there were drops of blood found inside the apartment, there was no evidence that any blood had been cleaned up, sources said.

No one has been named a suspect in the case, but Lori's husband, Mark Hacking (search), has been labeled a "person of interest."

In other news Wednesday, a convenience store clerk may have been one of the last people to see Lori Hacking before she vanished, according to reports in the Deseret Morning News and on KSL NewsRadio.

The clerk at a convenience store near the couple's apartment, who was not identified, said Mark and Lori Hacking came in between 6 p.m. and 9 p.m. July 18, the day before Lori was reported missing.

The source told the radio station that Mark Hacking was talking with the clerks and seemed happy, but his wife did not seem happy. The clerk said Mark visited the store several times a week and asked employees not to tell his wife he was buying cigarettes.

Meanwhile, the search for Lori Hacking was winding down as hope she would be found alive faded.

The families of Mark and Lori Hacking on Wednesday shut down their volunteer command post at a Mormon meeting house after calling off an organized search of neighborhoods, industrial areas and nearby canyons.

Police with cadaver dogs turned up no clues to the pregnant woman's whereabouts in an early morning search.

The canine crews found "nothing of consequence" at the municipal landfill before breaking off for the day, but they have not finished methodically churning up 15 feet of garbage and dirt over a wide area, Detective Phil Eslinger said Wednesday. The search was conducted overnight because the dogs work more effectively in the cooler air, authorities have said.

The voluntary community search for Lori Hacking had been called off Tuesday, eight days after her husband, Mark, reported that she had not returned from an early morning jog.

Organizers said the search was moving from neighborhoods, industrial areas and nearby canyons into more rugged terrain, and they did not want volunteers getting hurt.

The volunteer search could resume later using specialized teams or specific tips, and all-terrain vehicles and helicopters could be deployed as needed, according to Scott Dunaway, a spokesman for Lori Hacking's family.

Husband Still Silent

Mark Hacking, 28, who has been hospitalized since last week in a psychiatric unit, has retained high-profile defense attorney D. Gilbert Athay, who deployed his own team of investigators on Tuesday.

Athay said he has spoken to Mark Hacking many times since he was hired last week, but refused to characterize the conversations.

Assistant District Attorney Bob Stott said Mark Hacking is free to leave the hospital. Hacking did not return a phone message left Tuesday with an administrator at the University of Utah hospital.

Earlier this week, police confirmed that a bloody knife with strands of brown hair on it was among the numerous pieces of evidence they removed from the couple's apartment.

There were also unconfirmed reports that authorities were testing a clump of brown hair found in a trash bin just a block or two from the store where Mark Hacking purchased a mattress minutes before he called police about his wife's disappearance.

On the day the Lori disappeared, authorities were seen removing a box spring from the couple's apartment. Investigators have refused to confirm reports that they found a mattress in a nearby trash bin the same day.

Detective Dwayne Baird would not say Tuesday if police recovered a mattress, although he did say investigators are not looking for one.

Also Tuesday, police completed their search of the apartment. The families of the missing woman and her husband began packing up and moving out the couple's possessions.

The couple were planning to leave their Salt Lake City home last week and move to North Carolina, but Lori Hacking disappeared just days before, apparently on July 19. Lori had just learned she was five weeks pregnant.

After she vanished, police and family members learned that besides lying about being accepted to medical school, her husband had not even graduated from college.

"We learned a lot of things in his life that are not true," Baird said Tuesday. "Medical school was the pinnacle of that deception."

Disturbing Phone Call

In other developments, police confirmed news reports that Lori Hacking's last day at work before she disappeared was cut short by a phone call that left her so distraught she went home early.

"We wouldn't have any reason to doubt" the employee accounts, Baird said Monday.

Hacking's co-workers said Lori was sobbing after the University of North Carolina (search) medical school called to say her husband was not enrolled there, as he had told her he was. Lori had been trying to arrange on-campus housing.

Colleagues at Wells Fargo Securities Services (search) said Lori, a trading assistant, was a normally private young woman who did not share personal troubles, making her breakdown in the office all the more unusual.

The co-workers gave accounts of the phone call to homicide detectives after she was reported missing. Officials at the University of North Carolina were trying to determine whether one of their administrators made the call.

Church said detectives showed up at Wells Fargo the day after Hacking's disappearance and inspected her e-mail and computer files. Results on some of the other evidence collected by police are pending.

"She was visibly upset. She started to cry and got up to walk away," her supervisor, Randy Church, told The Associated Press on Monday.

He added that when co-workers asked her what was wrong, she replied, "It's no big deal; I'm OK. But I think I will go home."

Lori Hacking left work early after receiving the call Friday afternoon, July 16. Mark Hacking reported his wife's disappearance the following Monday.

Mark Hacking said his wife did not wake him up after coming home from an early morning jog July 19 and never showed up to work.

Police later said he was at a furniture store buying a new mattress only about a half an hour before reporting that Lori was missing.

Footage from a surveillance camera shows Mark Hacking looking for a mattress in one store but then leaving, apparently when he found out he couldn't take his purchase with him right then, FOX News has learned.

Instead, he wound up buying the mattress he came home with from a store across the street.

Mark Hacking has been at the psychiatric hospital since police found him running around naked in sandals the night after the search for his wife began.

FOX News' Alicia Acuna, Catherine Donaldson-Evans, Carol McKinley and The Associated Press contributed to this report.