VIDEO: Calif. Sex Offenders Wore Ankle Monitors During Murders

Convicted sex offenders who authorities in Southern California believe raped and killed four women allegedly wore GPS trackers while committing their crimes, and investigators believe there may be more victims.

Anaheim police Chief Raul Quezada told Fox News Monday that Franc Cano, 27, and Steven Dean Gordon, 45, were wearing ankle tracking bracelets when the women were assaulted and killed last fall and earlier this year. The chief added that data from the devices "was one of the investigative tools we used to put the case together." Authorities at the news conference did not explain how Cano and Gordon allegedly managed to carry out the killings while under supervision.

Anaheim police Lt. Bob Dunn earlier said the two were complying with a requirement to check in monthly with authorities and police had no reason to watch them more closely and hadn't received any such request from other agencies.

The Orange County district attorney's office said Cano and Gordon, who were arrested Friday, were each charged with four felony counts of special circumstances murder and four felony counts of rape. If convicted, the men could face a minimum sentence of life without parole or the death penalty. They were being held without bail and expected to be arraigned today.