On Christmas Eve, the leaders of a Denver mosque sent an e-mail to the U.S. Department of Homeland Security to express concerns about a man who was becoming radicalized.

The e-mail, which was obtained by The Denver Post, describes a white man from Texas who had attended a luncheon for recent converts and an open house where he rebuked a presenter for being soft and told others that it is OK to fight to establish the rule of Islam in the United States.

The e-mail appears to be about Joshua Andrew Cummings, the 37-year-old accused of shooting and killing a private security guard working for Denver’s Regional Transportation District.

Cummings has not been formally charged but is being held without bond in Denver’s Downtown Detention Center. He is scheduled to appear Friday in Denver District Court.

Police have said that Cummings approached Scott Von Lanken, 56, outside Union Station as he was giving directions to two women. The suspect pointed a gun at Von Lanken’s neck and told him to follow directions, and he then pulled the trigger.

Police said Wednesday they did not know of a motive.

Cummings, a former Army sergeant, recently came to Denver from Pampa, Texas, where he ran a Brazilian-style jiu-jitsu studio. His social media postings are filled with references to Islam, police brutality and the failing of the United States.

The leaders of the Denver mosque feared that he was becoming radicalized. They decided to inform homeland security and sent pictures and videos of the man, whom they only knew as “Joshua.”

The mosque leaders told federal authorities that they were arranging meetings between the man and imams to try to mellow him.

“But I doubt it would help,” the e-mail said. “He is not listening to reason.”

Denver civil rights attorney Qusair Mohamedbhai, who spoke on behalf of the mosque’s leaders, said it appeared law enforcement took the alert seriously. The leaders thanked federal authorities for their professional and prompt response to the concerns.

“The local Muslim communities cherish their relationships with their neighbors and local, state, and federal law enforcement, and will always oppose those who undermine our collective American values,” Mohamedbhai said in a statement.

It is unclear when Cummings moved to Colorado from Texas. He had been living at the Holiday motel in Englewood with a woman and a young child. Cummings’ social media posts indicate he is married and that his wife also practices Islam.

The Holiday motel manager said Cummings first stayed there in the fall but left after a month. He returned around the New Year.

The manager, who spoke to The Denver Post on the condition that his name not be published, said Cummings was a no-problem tenant, who sometimes helped other renters pay their weekly fees.

“He tried to keep his good deeds on the down low,” the manager said. “I never had any thoughts that he was violent or anything like that.”

Back home in Texas, Cummings had been drawing attention to himself as his opinions about Islam grew stronger, according to several people who knew him.

Maggie Johnson, a reporter for the Pampa News, said Cummings started writing martial arts stories for the newspaper in 201,5 but his ties to the newspaper were severed when he became obsessive about bullying and conspiracy theories at the local high school.

“He wrote guest pieces. He was little off,” Johnson said. “He got really obsessively concerned about the topic of bullying.”

On his Twitter feed, Cummings earlier postings mostly focused on jiu-jitsu. However, he increasingly began posting about Islam, police violence and conspiracy theories such as an implant that would take away a person’s desire for God.

Many of his Twitter posts link back to a Facebook page that has been disabled.

Troy Schwiegerath, who splits time between Denver and Pampa, told The Denver Post on Wednesday that Cummings briefly trained at his jiu-jitsu studio and the opened a rival dojo in town.

Cummings began posting Islamic teachings at his academy and on Facebook, Schwiegerath said. Cummings also visited Pampa churches, saying they should be teaching the Koran.