Steven Zelich, 52, who was arrested Wednesday, had not been charged with homicide. He was scheduled to appear in court Friday afternoon.
The bodies of Laura Simonson of Farmington, Minn., and another woman whose identity has not been released were found June 5 by roadworkers in Geneva, Wis., a town near the Illinois line and about 40 miles southwest of West Allis, the Milwaukee suburb where Zelich lived.
Zelich allegedly told investigators he met the unidentified woman online in 2012 and caused her death during a meeting with her. He said he stored her body in his home for about a year and then transferred it to his car.
Investigators say that Zelich had posted on websites catering to sadomasochists.
Simonson, 37, was allegedly killed during an encounter in Rochester, Minn., in November. She was reported missing Nov. 22.
Police said Simonson was gagged and had a rope around her neck. The other woman's hands were tied behind her.
Sources in the West Allis Police Department said Zelich was forced out in 2001 because he had a fight off-duty with a prostitute. He had worked as a police officer there since 1989.
Since 2007, Zelich had worked as a licensed security guard.
Minnesota police have found evidence that Zelich stayed with Simonson at the Microtel Inn and Suites in Rochester on Nov. 2 and Nov. 3, Rochester Police Capt. John Sherwin said. Sherwin said there was also evidence that Simonson died in there and that Zelich was alone when he checked out.
"Basically, after Nov. 2 she was never seen from or heard from again," Sherwin said.