A St. Louis County woman was slain for her car, which the killer soon traded for methamphetamine, according to a search warrant filed this week in Ramsey County.

Cristyna Leah Watson had been missing for nearly a month, before her body was found Thursday in rural Cloquet, Minn. Authorities say an acquaintance now jailed in connection with a gang-related assault is the slaying suspect.

Watson, 25, was from Floodwood, about 45 miles northwest of Duluth. She was last seen by her family on Sept. 8, and Floodwood police put out a missing-person alert in late September.

An anonymous caller told police that a couple who knew Watson had been planning to kill a young woman for her car.

Watson's gray 2005 Pontiac Grand Prix and her cellphone also were missing, but both since have been recovered. The search warrant filed Monday in St. Paul says the car was recovered outside a Newport bar and impounded so it could be searched.

An affidavit alleges the slaying happened this way:

On Sept. 29, Watson's car was involved in a gas drive-off near Grand Casino in Hinckley. The gas was pumped by a woman wearing a black hoodie who later was identified as an acquaintance of Watson's and who was eventually located in the Carlton County jail.

The woman told investigators that a friend of hers had admitted that he lured Watson to a garage to get some drugs, then hit her twice in the head with a hammer to take her car.

The woman told police that Watson didn't go down and instead asked the man what he was doing, so he choked her. He claimed that he took Watson's body to a swampy area, a quarter-mile into the woods, she told police.

The woman had Watson's cellphone when booked into the jail, the affidavit says.

The car was spotted at Mystic Lake Casino & Hotel in Prior Lake, driven by a woman who allegedly traded 2 ounces of methamphetamine to the suspect for it.

An agent for the Minnesota Bureau of Criminal Apprehension went to the hotel and interviewed her. She said she was nervous about driving the car and abandoned it in Newport.

At the behest of the BCA agent, the Washington County Sheriff's Office towed the car to BCA headquarters in St. Paul for evidence analysis.

Joy Powell • 651-925-5038