The University of California, Los Angeles resumed its in-person classes on Wednesday following a former lecturer's arrest on suspicion of making threats against the school, The Associated Press reported. 

UCLA canceled in-person classes on Tuesday after Matthew Harris, 31, was taken into custody from his apartment in Boulder, Colo., following a standoff that ended peacefully, AP reported.

The former philosophy department instructor had sent an email to some of his former students Sunday that police said led them to believe Harris was “potentially planning for a mass violence or shooting event at UCLA,” according to AP.

Harris had been placed on leave from the university last year. A philosophy professor at the university system's Irvine campus was granted a restraining order against him after he sent emails to his mother threatening to "hunt" the professor.

AP reported that the police chief in Boulder, Maris Herold, said officials reviewed a manifesto that identified "thousands of references to violence, stating things such as killing, death, murder, shootings, bombs, schoolyard massacre in Boulder and phrases like ‘burn and attack Boulder outside of the university.’”

Herold added that authorities had contacted Harris in October but no criminal charges were filed at that time, saying the department is now reviewing their reports from that encounter.

Federal charges are pending against Harris, who has been transferred to federal custody. AP reported that it was not known if Harris had an attorney.