A man who was under investigation for suspected interest in Islamic extremism was convicted Tuesday of sending pornographic images to a 15-year-old girl and trying to coerce her to respond in kind.

Seitu Kokayi, 30, had taught the girl at an Islamic school in D.C. since she was 6 or 7, according to trial testimony. But over several weeks in August, when she was visiting family in Minnesota, he began engaging her in sexual conversations and video chats.

Federal law enforcement officials had obtained a secret wiretap on Kokayi’s phone based on classified intelligence, according to court filings. Prosecutors previously produced evidence that Kokayi shared extremist propaganda with the girl and other students, but they did not raise those allegations at trial.

Prosecutor Kellan Dwyer described Kokayi as a “wolf in sheep’s clothing,” a “trusted teacher” who used that relationship to pressure the girl to engage in sexual activity. In text and phone conversations shared in court, he asked her to show him parts of her body and whether she would marry him.

Defense attorney Mark Petrovich argued that although the relationship was “inappropriate” and “wrong,” it wasn’t illegal.

“There’s no evidence that he asked her to show anything that would rise to the level of child pornography,” he said.

At the bench trial, Judge Leonie M. Brinkema said she would rule later on one charge: whether Kokayi tried to persuade the girl to have sex with him.

In a filing early in the case, Dwyer accidentally revealed through a copy-and-paste error that WikiLeaks founder Julian Assange has been charged under seal. However, officials say the two cases have no connection.