The Texas Education Agency has opened an investigation into a Grand Prairie teacher after learning he faces criminal charges in Oklahoma, officials said Thursday.

Christopher Durham was arrested in 2013 and accused of threatening that he was capable of a Sandy Hook-like shooting. He was placed on leave this week from his position at Grand Prairie Collegiate Institute after concerns about his past were discovered by students who researched him online.

Durham, 46, said the criminal misdemeanor charges against him are false. He has not been convicted of any crime and awaits trial in November.

TEA spokeswoman DeEtta Culbertson said Thursday that the State Board of Educator Certification was beginning its disciplinary case to determine whether Durham can continue to teach in Texas. She did not elaborate.

Durham told The Dallas Morning News on Thursday that he wasn't aware of any investigation of him by state authorities. He said the idea of such an inquiry is an attempt to cast an "aspersion to my character."

Durham said he had discussed the pending charges with state education officials when he initially applied for his Texas certification, telling them, “There’s nothing to it.” He was first certified to teach in the state in August 2014.

Culbertson said state law prohibits her from commenting on what the state knew about Durham’s criminal background. In general, however, she said criminal histories are evaluated case-by-case.

According to the TEA website, the state considers various factors of a person’s criminal background in deciding whether to certify him or her, such as the nature and severity of any charges.

Christopher Durham has been charged by the Oklahoma County district attorney's office with one count of threatening an act of violence to do physical harm.

Durham previously taught in Oklahoma. Generally, out-of-state teachers apply for certification in Texas by filling out an online application, submitting college transcripts as well as certificates, and paying $164. The state then reviews the credentials and test scores for comparable out-of-state certification tests, and conducts a background check.

Durham is accused of making threats against a judge and attorneys during his divorce case. According to an affidavit, he told his attorney that the judge and his wife's attorneys didn't realize he was "capable of doing things along the line of what just happened in Newtown, Connecticut." Twenty children and six adults were killed at Sandy Hook Elementary in Newtown in December 2012.

Students researching Durham found articles linked to his arrest and alleged threats. Durham said Thursday that a Google search should not trigger a re-evaluation of his teaching credentials.

“You don’t go through the court of public opinion [that] you might find on the internet,” he said. “Kids will look people up on the Internet. It’s a churlish thing to do. It’s workplace bullying. It’s inappropriate.”

This was Durham’s first school year in Grand Prairie, where he is now on administrative leave. Before that, he had worked in the Fort Worth school district, where concerns about his past also became an issue.

Fort Worth ISD spokesman Clint Bond said this week that after the district learned in 2015 about the alleged comments regarding Sandy Hook, they began making arrangements to fire Durham. But "after consultation with his representative, he was allowed to resign," Bond said.