Former Eastern Michigan University football star turned Oklahoma City Police Officer Daniel Ken Holtzclaw was arrested Thursday on charges of serial rape, after police say he sexually assaulted at least seven women over a six-month period while serving as an on-duty officer.

The 27-year-old Oklahoma City police officer is accused of raping at least seven women from February 2014 to June 2014 while on duty, and is being held in lieu of $5 million bond. Holtzclaw is a native of Enid, Oklahoma, and attended EMU on a football scholarship from 2005 - 2008.

The case started after one woman came forward and accused Officer Daniel Holtzclaw of "sexual impropriety" during a traffic stop, Oklahoma City police Capt. Dexter Nelson told CNN. After the first woman's complaint, investigators started looking into all of Holtzclaw's traffic stops for other potential victims, and so far, six others have been identified.

The arrest warrant alleges that Holtzclaw is being held on nine counts, including suspicion of first-degree rape, rape by instrumentation, three counts of forcible oral sodomy, two counts of sexual battery and two counts of indecent exposure. Charges in the case are expected to be filed by next Friday. Holtzclaw could face life in prison without the possibility of parole for the charges.

"We received a complaint and also uncovered a number of other individuals, females, that had experienced the same thing with this officer," Oklahoma City Chief of Police Bill Citty said during press conference.

"All his victims were black females and they range in the ages of 34 to 58. Right now I've identified seven (women), six of whom we've received statements from and one we're still attempting to get statements from. So you have seven total over a period of five or six months."

Holtzclaw had been working with the OCPD for three years, according to Citty, and evidence points to all of the incidents occurring during his 4 p.m. to 2 a.m. shift while he was on duty.

"The types of acts committed were anywhere from just requiring the females expose themselves, to fondling the females, and...actual intercourse," Citty said. "About three of the victims were asked or required to perform oral sodomy on this officer."

"We kind of anticipate there may be more victims out there because this goes back to February -- February was the earliest that we have here, through June," Oklahoma City Police Chief Bill Citty told reporters.

"If there's anyone that was victimized by this officer, we certainly want to hear from them."