TULSA COUNTY, Oklahoma - A Creek County man was in federal custody Tuesday after being accused of sexually abusing an eight-year-old girl and a ten-year-old boy.

The Justice Department said he took sexually explicit photos of the kids and shared some of them online. The affidavit said an undercover FBI agent was on the Kik messaging app, searching for child predators when the agent received a message from Ryan Miller.

It said Miller sent sexually explicit photos of and eight-year-old girl to the agent and gave a detailed description of the sexual abuse.

"One of the things that struck me the most when prosecuting these cases is when an undercover officer posing as a 14 year old makes a post it's often seconds go by before she's being solicited for sex acts by adult me.,” said Northern District of Oklahoma Assistant U.S. Attorney Chris Nassar.

The affidavit said one of the messages Miller sent to the undercover agent said Miller had been working on expanding the sexual relationship with the eight-year-old girl for the last few months, but it was progressing slowly.

"We have an entire initiative dedicated to protecting children and stopping child molesters and child exploiters," said Northern District of Oklahoma U.S. Attorney Trent Shores.

The affidavit said Miller was arrested, he admitted to sexually abused a ten-year-old boy at least 20 times and sexually abused ?an eight-year-old girl at least four times and took at least 50 sexually explicit pictures of the victims.

"Every day there's more messaging applications. Every day there is a new popular one with kids in school so every day the officers are constantly trying to keep up with the change in technology and the change in popularity of various apps," said Northern District of Oklahoma Assistant Attorney ?Chris Nassar.

Miller’s attorney declined to comment.