Two convicted sex offenders accused of murdering at least four women in California were literally on the government's radar the whole time—police say the men, who checked in with probation officers on a regular basis, were both wearing court-ordered GPS ankle devices.

Franc Cano, 27, and Steven Dean Gordon, 45, were both arrested on Monday and charged with murdering four Orange County women: 21-year-old Jarrae Nykkole Estepp, 20-year-old Kianna Jackson, 34-year-old Josephine Monique Vargas, and 28-year-old Martha Anaya.

Police say starting last October, Cano and Gordon attacked, raped, then murdered the women—charges that could subject them to the death penalty if they are found guilty.

But according to authorities, Cano and Gordon were under surveillance the whole time—both men were checking in with parol officers once a month and wearing court-ordered GPS devices—Cano's from a state court and Gordon's from a federal judge.

Local officers began to suspect the deaths were all related after discovering Estepp's naked body laying on the conveyor belt of an Anaheim trash facility. Based in part on GPS and cell phone signals, police eventually tracked down Cano and Gordon, who were living out of their car.

"The GPS was in fact intact, attached to these suspects during the commissions of the crimes," Anaheim Police Chief Raul Quezada said during a press conference Monday.

Cano and Gordon, who both served time for sex crimes against a child under the age of 14, were required to wear the ankle bracelets as part of their probation. According to reports they met in 2012 when they cut off the GPS devices they were wearing at the time, took a Greyhound to Vegas and lived under aliases. They were rearrested but do not appear to have been imprisoned for the violation.

[image via AP]