A Walmart employee first noticed the man on July 2 at about 4:45 p.m. in New Lenox. The employee told police it looked like the man was taking inappropriate photos of a female customer.
The employee confronted the suspect, and he ran away, police said.
On July 18, the same employee noticed the suspect taking photos of children using a key fob device.
"She saw the same guy again and she alerted the security department," Police Chief Louis Alessandrini said. "They were able to follow him inside the store and witness him with a device in his hands taking pictures of various females adults and juveniles inside the store."
Police arrived and arrested 61-year-old Paul T. Raibley. He was already a registered sex offender for similar crimes dating back to 1998.
Investigators said a small camera was disguised as a key fob.
Police said they found videos of the woman and photos of children on devices owned by Raibley.
Officials also found more videos of juveniles in public places at his Joliet home.
He was charged with three counts of child photography by a sex offender and one count of unauthorized video recording.
He was taken to the Will County Adult Detention Facility.
A judge denied Raibley's pre-trial release. He is due in court on July 31 at 9 a.m.
Walmart released the following statement:
"The safety of our associates and customers is a top priority. We're deeply disturbed by the allegations and are working with authorities as they continue their investigation."