"I want to grow old with you, but I can't do it under these conditions," she wrote.

The typewritten letter was found on a shelf in a spare bedroom of the couple's apartment about the same time an officer pulled a blood-stained hunting knife from a bedside drawer.

Within hours, police were confident that Lori Hacking had been murdered.

Found during a routine search of the Hackings' apartment on July 19, the letter indicates Lori was troubled by her marriage, which friends and family members had described as nearly perfect.

"I hate coming home from work because it hurts to be home in our apartment," she wrote. "I can't imagine life with you if things don't change . . . I got someone I don't want to spend the rest of my life with unless changes are made."

Although police do not know when the letter was written, it could relate to Lori's July 16 discovery that Mark had been lying about his educational ventures.

The letter was one of scores of items cataloged in four search warrants made public Wednesday afternoon in 3rd District Court.

Among the most potentially damaging items seized was a pillow with a "washed out brownish colored stain" found in the Dumpster behind the Hackings' apartment complex. Mark would later tell his brothers he shot his wife with a .22-caliber rifle as she slept.

The knife, according to prosecutors, was used to cut off the top of the couple's mattress. Detectives recovered the mattress from a Dumpster in a nearby church parking lot but have not found the top.

According to the search warrants, police were immediately suspicious of Mark's purchase of a queen-size mattress just minutes after he called them in a panic to report Lori missing.

When asked about that purchase, he allegedly told investigators he had thrown out the old mattress a month earlier because his wife had bled on it during menstruation.

Employing several warrants on multiple days, starting the day Lori vanished, investigators searched the Hackings' vehicles, their apartment and the psychiatric institute where Mark worked. They also took fingerprints and samples of Mark's blood.

Their collections - from a blood-stained carpet sample to DNA samples from Lori's underclothing - prompted the Salt Lake County district attorney to charge Mark Hacking with first-degree felony murder and obstruction of justice Monday. Mark Hacking's July 24 confession to his brothers also was a major basis for the charges.

District Attorney David Yocom said he believes the evidence is sufficient to prove Mark Hacking's guilt without two other key pieces of evidence: Lori's body and the murder weapon.

Nonetheless, investigators plan to return tonight to a west Salt Lake County landfill to continue searching for Lori's remains and the weapon. It will be the tenth night of searching the 3,000-ton pile of trash collected and dumped on July 19 and early July 20.

Salt Lake City police spokesman Dwayne Baird said the search - and all other investigative efforts - will now fall under the direction of county prosecutors, though he doesn't believe any changes have been directed.

"As far as I know, we're doing the same thing," he said.

In past efforts, excavators using a backhoe have separated small portions of the refuse from the pile in order to give cadaver dogs from Duchesne County a better chance to sense human remains.

Meanwhile, police officers and other emergency personnel have scanned the trash seeking "landmark" pieces of refuse that might indicate they are approaching the trash that was collected near the Hackings' apartment and the University Neuropsychiatric Institute, where Mark Hacking worked as an orderly and allegedly dumped his wife's body.

UNI employees told The Salt Lake Tribune that investigators expressed interest in surveillance tapes recorded the morning of Lori's disappearance. A security-camera company executive told The Associated Press that police are starting to review images taken by 16 motion-sensitive closed-circuit cameras in and around the institute.

Baird downplayed reports that the tapes show Mark Hacking putting his wife's body into a Dumpster. "I'm guessing that it's not what they think it is," he said.

The search warrants show that police were investigating Lori Hacking's disappearance as a homicide from the beginning, despite repeated public pronouncements that it was a "missing person" case and that Mark Hacking was simply a "person of interest."

As thousands of searchers prepared to muster at City Creek Canyon, where Hacking claimed his wife went for a morning jog without returning, Detective Vic Siebeneck was asking for a warrant from state Magistrate Timothy Hanson.

In the application, Siebeneck wrote that he believed a search of the Hackings' cars and apartment would produce "weapons, implements, tools and other fruits or instrumentalities of the crime of homicide."

mlaplante@sltrib.com