(CHICAGO) A Chicago Police officer who was employed as a security guard at a Chicago Public School has been charged with having a sexual relationship with an underage girl who attended the high school where he worked.

Eugene Ciardullo, 51, was charged with one felony count of criminal sexual assault of a victim between 13 and 17 years old.

The student, who is now 18, admitted to authorities that she had a sexual relationship with Ciardullo when she was 17.

Ciardullo befriended her during the 2014-2015 school year, when she was a 16-year-old sophomore, Cook County Assistant State’s Attorney Ed Murillo said in bond court on Sunday.

Michael Passman, a spokesman for CPS, said Ciardullo immediately resigned after he was removed from his position at the Chicago High School for Agricultural Sciences on Dec. 15.

“A part-time security officer . . . was removed from his position in December in response to the serious allegations, and the individual is no longer an employee of Chicago Public Schools,” Passman said in an emailed statement. “The school responded promptly and followed proper protocols after it became aware of the allegations, and CPS is cooperating with the law enforcement as it investigates the matter.”

The school district has also offered support services for member’s of the school community, Passman said.

Ciardullo and the girl exchanged phone numbers and chatted on social media websites during the summer after her sophomore year.

In September 2015 — during her junior year — Ciardullo told her through the social media site Snapchat that he had feelings for her. Less than a month later, he told her he loved her, Murillo said.

The relationship soon became physical and carried on from February through December 2016, with Ciardullo meeting the girl — then 17 — for sex in an empty parking lot and motel rooms, Murillo said.

During July and August, Ciardullo — a Marine Corps veteran — began personally training the girl in preparation for a physical fitness test to enter the Marines, Murillo said.

The two discussed their age difference, and Ciardullo told the girl he “could lose his job and go to jail if they were caught,” Murillo said.

Ciardullo told the girl to “tell people who asked about their relationship that they were just good friends,” Murillo said.

One of the girl’s relatives confronted Ciardullo in late November after learning of a text exchange between the two, and Ciardullo admitted they were having an affair, Murillo said.

In mid-December, CPS investigators met with the girl and — after being confronted with photos of the two kissing — admitted they had been in a sexual relationship.

On Friday, police arrested Ciardullo at his home in the 8300 block of South Keeler in the Ashburn neighborhood. Ciardullo also admitted the two were in a sexual relationship and that he knew she was a minor at the time, Murillo said.

On Sunday, Cook County Judge Maria Kuriakos Ciesil set bail at $75,000 for Ciardullo and ordered him, should he be released on bond, not to have contact with the victim or anyone under the age of 18; to surrender his passport and his Firearm Owners Identification card; and not use the internet.

Ciardullo, who has been with the department for 21 years, was assigned in the Deering District, according to police.

“The Chicago Police Department is currently also investigating this incident internally and administratively. We remain committed to the highest levels of accountability for our officers and members and will not tolerate any activity or actions that undermine the integrity of the hard working men and women of our Department,” according to a statement from police spokesman Anthony Guglielmi.