PORT ST. LUCIE, Fla. -- Federal officials arrested a Port St. Lucie police, Florida officer Tuesday in connection with a child pornography investigation, reports CBS affiliate WPEC.

Officer Michael Harding, who in 2011 was named "Officer of the Year" in Fort Pierce, Fla., joined the Port St. Lucie Police Department in 2012. Department of Homeland Security agents have been investigating Harding since July, when an undercover agent first encountered a user on an online Kik Messenger group, who allegedly posted two photos of a preteen female engaging in a sex act, according to a criminal complaint.

That user, who went by the name "desthfromabovee," was allegedly Harding.

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The undercover investigator said "desthfromabovee" posted more pictures a week later. And in August, the investigator said the user posted in a Kik Messenger chat room a sexually explicit video of another young girl engaged in a sex act, according to the criminal complaint.

Investigators served a summons on the account for "desthfromabovee" in August. The person who set up the account used the name Mark Powers, according to the criminal complaint.

Homeland Security then obtained phone records from AT&T, which helped authorities track the user name, Kik Messenger app, IP address and cell phone service back to Harding.

He allegedly accessed the "desthfromabovee" account on Kik 33 times, most often during the early morning hours between midnight and 6 a.m.

Investigators said Harding worked the 10 p.m. to 8 a.m. shift for the Port St. Lucie Police Department, Saturday through Tuesday.

Based on the time frames of the posts and his work schedule, investigators believe Harding uploaded some of the pornographic content while in his patrol car.

Investigators searched Harding's home and found two thumb drives, one stored in a gun case in a closet in the master bedroom. That drive allegedly had hundreds of images and videos of children "engaged in sexually explicit conduct," according to the criminal complaint.

A second drive allegedly included images of Harding and explicit photos of prepubescent girls.

Harding faces federal charges for receiving and distributing material involving sexual exploitation of minors, and possession of child pornography.