OKLAHOMA CITY » An Oklahoma City police officer arrested on charges of serial sexual assault preyed on women in the rundown neighborhoods he was assigned to patrol — picking some up off the street, pulling others over at traffic stops and in one case taking a woman to a nearby school, police documents show.

Former star football player Daniel Ken Holtzclaw, 27, raped one woman and either fondled others or forced them to expose themselves, investigators said Friday. He made others perform sex acts on him. Three were assaulted in his car and one was taken to a school in the Spring Lake Division where he worked, according to the affidavit.

And police said there could be more victims than the seven already identified.

"They’re retracing all of his contacts, as many as they can, especially traffic stops," said police spokesman Capt. Dexter Nelson.

The investigation began — and Holtzclaw was immediately placed on leave — when police said a woman complained in June that Holtzclaw had sexually assaulted her during a traffic stop on a boulevard about two miles north of the state Capitol. The alleged incident prompted police to check other contacts Holtzclaw had with the public since beginning street patrols about 18 months ago.

Officers identified seven victims and eight incidents before accusing Holtzclaw of crimes including rape, sexual battery and indecent exposure. Police Chief Bill Citty published Holtzclaw’s photograph with the hope that other women would step forward, he said.

District Attorney David Prater said formal charges could be lodged by Aug. 29. Holtzclaw had not previously been disciplined in his three-year tenure with the department.

He was being held at the Oklahoma County Jail late Friday in lieu of $5 million bond, according to jail records. No attorney is listed for him and jail staff said they could not provide attorney information.

Police reports said the victims were all black women between the ages of 34 and 58, though police said it wasn’t clear if Holtzclaw targeted victims because of their race.

"All of this victims were black, but that is probably because the area where he worked," Nelson said, referring to the mixed-race neighborhood of mostly black, Hispanic and Vietnamese residents.

Holtzclaw joined the force after graduating with a criminal justice degree from Eastern Michigan University. He was also a standout football player.

In high school, he was an all-state player in his senior year at Enid, leading the team with 123 tackles.

His former high school football coach, Tom Cobble, said the allegations were "absolutely a shock."

"It’s so totally out of character. It’s unbelievable." said Cobble, who retired from coaching at Chickasha, Oklahoma last year.

The Eastern Michigan football media guide in 2008 featured him at the top of its roster page — touting his weightlifting abilities and his starting in every game since his arrival on campus in 2005.

He tried out for the Detroit Lions after he was not taken in the NFL draft, but he was cut from the team.

Nelson said Holtzclaw’s colleagues were upset at the allegations against a police officer.

"Most of us see it as a black eye to our profession and our department," he said.

Associated Press reporter Ken Miller contributed to this report.