Shortly after 8 a.m., Walworth County authorities showed up at Zelich's apartment building in West Allis, Wisc., entering the unit with a battering ram, according to residents.
Law enforcement sources said Zelich, 52, worked for the suburban Milwaukee Police Department until 2001.
The case started on a Walworth County highway near the town of Geneva in early June, when a lawn cutting crew found abandoned suitcases containing the bodies of two women.
One of the victims, Laura Simonson, has been identified. Simonson, a mother of seven young children, was reported missing Nov. 22, 2013 by her family in Minnesota.
An anonymous internet posting with photos of the victim claims she had been recruited as a sex slave and held in bondage for the past few months; but the I-Team doesn't know who posted this information or on what basis they made those claims. The victim's family members said they also don't know who posted the information.
The suspect has not been charged, although his identity has been released. A second victim remains unidentified.
Read the Walworth County Crime Stoppers' description of the unidentified victim here.
Read the Geneva police press release about Zelich's arrest here.