A security team leader at Richard Montgomery High School has been arrested for sexual abusing a student at the school, Montgomery County police said. 

Police said Mark Yantsos, 57, had an ongoing sexual relationship with a 17-year-old student at the same school where he'd been the head of security for a decade. They said he bought her gifts and a phone, so they could talk after school, and last month, he picked her up and took her to a hotel where the two had contact that police called "inappropriate."

It turns out, the Rockville man may have a criminal past. 

A New York Times article online reports Yantsos was arrested for menacing a waitress at a topless bar with his gun when he was part of the NYPD more than 20 years ago. The NYPD confirmed to WUSA9 that Yantsos was a sergeant, but they couldn't say what came from this reported arrest or why he left the department. 

Montgomery County Public Schools found out about the allegation after looking up his name online, but only after Yantsos was arrested for sexually abusing a student this week. 

MCPS said in 2007, Yantsos passed their background check.

Yantsos not only was in charge of keeping hundreds of students safe at Richard Montgomery High School, but he was also a long-time coach of the Maryland Lightning, a basketball team made up of teen girls. WUSA9 emailed the Maryland Lightning basketball team to ask what checks had been made into Yantsos' background. We're still waiting to hear back.

A female voice told us, "I'm not going to open the door," when WUSA9 knocked on the door of Yantsos' Rockville home.

"I never would have imagined this would have ever happened," said neighbor Arup Sen, who was shocked.

Yantsos was arrested Thursday morning at his home on a Montgomery County criminal warrant. He is being charged with sexual abuse of a minor and a fourth-degree sex offense.

MCPS said Yantsos is on administrative leave pending the outcome of the investigation. 

Detectives are asking all parents of students who attend Richard Montgomery High School to talk to their children about their interactions with Mark Christopher Yantsos and contact detectives at 240-773-5400 if they believe their child was victimized.

Montgomery County Public Schools released the following letter regarding the incident: 

“The allegations against Mark Yantsos, the security team leader at Richard Montgomery High School, are disturbing. As Principal Monteleone stated in his letter to the community (included below), the behavior described in the charging document “represents an irreparable breach of trust, ethics and the law.” Any adult who abuses their position and takes advantage of our students has no place in our schools or community.

“Additionally, it has come to our attention that in 1994, Mr. Yantsos was accused of using his revolver to menace a female while working for the New York Police Department. We have provided this information to the police.

“The safety of our students is paramount. In 2015, the Montgomery County Board of Education updated its policy regarding child abuse and neglect. Central to the updated policy are new practices, procedures and protocols to ensure students have a safe environment in which to learn. This includes:

• updated mandatory training of all full-time employees on recognizing and reporting child abuse; and

• the development of the Employee Code of Conduct, a document that summarizes the standards of conduct that MCPS and the broader community expect employees to follow.

We remain vigilant in our efforts to ensure all of our students are in a safe environment.”