A man who allegedly shot a private security guard in Denver on Wednesday was reported to the U.S. Department of Homeland Security by mosque leaders in December, when they expressed concerns that he had become radicalized. According to The Denver Post, the mosque wrote an email on Dec. 24 claiming that a white man from Texas—Joshua Andrew Cummings—had attended a luncheon for recently converted mulsims and that he told others in attendance he believed it was OK to fight to establish the rule of Islam in the U.S., along with other extremist views. Cummings is accused of killing Pastor Scott Von Lanken, who was working as a guard at Denver’s Regional Transportation District. Cummings has not yet been formally charged but is currently detained. Police have said they had not yet identified a motive in the shooting.