A Rockford rowing coach who admitted to secretly recording female athletes in various locker rooms had about 100 videos taken over a 4-½ year span and used a metal file to widen peepholes for a better view.

His home computer was filled with downloaded child pornography; search titles included phrases such as “young teen rough sex,’’ federal court documents show.

By all accounts, 30-year-old Timothy Warren Vallier was an exemplary high school crew coach with positive performance reviews. The women’s varsity crew team recently placed 8th in the country.

Crew teams could often be seen practicing on the Grand River near the Jupiter Avenue bridge in Kent County’s Plainfield Township. They used a state-of-the-art boathouse near West River Drive NE which opened in 2007.

Unbeknownst to legions of athletes who used its locker rooms, Vallier placed a hidden video camera inside the girls’ rowing team changing areas four to five times a season over the last several seasons, he told investigators.

“I’m more than shocked; it’s horrific,’’ Rockford Public Schools Superintendent Dr. Michael S. Shibler said Friday. “I’m so sorry for the parents and the students having to deal with this. And I’m angered and frustrated.’’

Two recent Rockford High School graduates helping coach the school rowing team in early July found a video camera in the team’s SUV outside the boathouse that was under Vallier’s control.

Images on that camcorder led to myriad criminal charges against Vallier, who was promptly fired.

The scope of the alleged criminal activity broadened on Thursday when federal investigators disclosed Vallier had also secretly recorded naked and partially-clad girls at the Rockford Freshman Center.

Vallier will appear Tuesday, Aug. 2 in U.S. District Court in Grand Rapids for a preliminary hearing and a detention hearing on federal charges that could put him behind bars for 30 years.

The Kent County Prosecutor’s Office on Friday dismissed five state charges so the case can be handled in federal court, where penalties are stiffer.

Rockford Public Schools has an eight-member security staff headed by a retired lieutenant from the Wyoming Police Department. It jumped into action July 8 after the former students called attention to the camcorder’s contents.

“We’ll go through anything and everything and research what can be done to make sure it never happens again,’’ Shibler said.

Details are spelled out in a criminal complaint filed in federal court by Timothy Kruithoff, a special agent with the U.S. Department of Homeland Security in Grand Rapids.

He says on July 8, two recent Rockford High School graduates who were helping coach the school rowing team found a video camera in the team’s SUV after obtaining the keys from Vallier, the head coach.

They knew Vallier sometimes video-recorded Rockford rowers competing and practicing for use as a training tool. They discovered several videos on the camera of girls from the team dressing and undressing in the changing room, Kruithoff wrote.

Hidden places:

“They saw a black circle around the edge of the recording which appeared as if the video had been shot through a peephole in the wall,’’ Kruithoff wrote. “They notified the school, which notified police.

“Officers responded and located a hidden compartment in the team changing room wall with two small holes drilled into it.’’

Vallier told investigators one hole was already there; he added a second hole and used a file to enlarge both “for a better view,’’ Kruithoff wrote.

“He stated that he placed a towel and a piece of cardboard inside the wall to position the camera against the holes,’’ the agent wrote.

Vallier consented to a search of his home on Cannonsburg Road NE on the edge of the village of Cannonsburg. Police seized his computer and cell phone.

A forensic examiner reported finding approximately 100 hidden camera video files from different digital cameras of girls changing clothes.

“Numerous underage victims were secretly recorded,’’ Kruithoff wrote. “In most of the videos, the girls were changing into or out of athletic clothing, getting completely undressed and exposing their pubic area unknowingly to the camera.’’

Vallier organized images and videos on his computer, categorizing them into files labeled with at least 15 different girls’ first names as well as a folder he labeled ‘to be sorted,’’’ Kruithoff wrote.

Time stamps on the videos ranged from 2012 to 2016 and showed at least two different locker rooms/changing rooms, the criminal complaint states.

Child pornography was also saved on Vallier’s computer, including images of prepubescent girls, court documents reveal. Numerous images show girls who appear to be between approximately 13 and 18 changing clothes and posing nude in a “lascivious manner.’’ Kruithoff wrote.

The investigator says he believes the images were downloaded from the Internet.

The computer also contained a series of Internet keyword searches for terms related to child pornography, including “teen schoolgirl nude,’’ “barely legal teen sex’’ and “young teen rough sex,’’ Kruithoff wrote.

Other computer files included Rockford rowing team rosters for multiple years which included team members’ names and birth dates.

The most serious of the two federal charges is attempted production of child pornography, which is punishable by a minimum of 15 years in prison and up to 30 years. The charge of possession of child pornography carries a maximum term of 20 years in federal prison.

The penalties are steeper than what he faced in state court; penalties for the five offenses range from five to 20 years with no mandatory minimum.

A federal conviction also carries a requirement for sex offender registration, a potential fine of up to $250,000 and financial compensation to the victims.

Vallier would also be subject to a lifetime of supervised release once he gets out of federal prison.

Shibler, the Rockford superintendent, moved quickly to protect students after criminal charges were filed in 63rd District Court. He got a court order banning Vallier from setting foot on school grounds.

“We’re going to evaluate everything that we found as a result of this case, including any procedures we can implement,’’ he said.

Shibler says he will brainstorm with staff to see if there is a way to detect hidden electronic devices, such as camcorders, before they are used for illicit purposes.

“If that technology exists, we want to use it,’’ Shibler said.