Federal authorities are investigating a note they said was written by the man being held in connection with the attack at the White House correspondents’ dinner that suggests he was angered by the actions of the Trump administration.

The writing was shared with The New York Times by two law enforcement officials who asked not to be named because they had not been authorized to disclose the information. The suspect, identified by the officials as Cole Tomas Allen, 31, of Torrance, Calif., is in custody and expected to be charged with multiple crimes in a court appearance on Monday.

It was uncertain on Sunday whether Mr. Allen had obtained legal counsel and close relatives could not be reached.

“I am a citizen of the United States of America,” the writing says. “What my representatives do reflects on me.”

In the next sentence, the writer alludes to allegations of sexual misconduct, saying that he is “no longer willing” to allow a “traitor to coat my hands with his crimes,” an apparent reference to President Trump though the writings do not mention him by name.

The writing does suggest that administration officials were the top targets.

“Administration officials (not including Mr. Patel): they are targets, prioritized from highest-ranking to lowest,” the writings read, apparently referring to Kash Patel, the F.B.I. director. It was not clear from the writing why Mr. Patel was singled out.

Secret Service are “targets only if necessary,” the writing says. Hotel security, Capitol Police and National Guard are “not targets if at all possible.” And hotel employees and guests are “not targets at all.”

Contained among the 1,000 or so words is an extensive list of apologies to his friends, students, family and others for his actions, as well as thanking them for their support throughout his life. It was not immediately clear where the authorities obtained the writing.

Anticipating the criticism that the attack might not be in line with Christian teachings, the writing appears to refer to reports of abuse in immigrant detention camps, the recent lethal attacks on boats in the Caribbean Sea and eastern Pacific Ocean and the bombing of an elementary school in Iran, among other things.

“Turning the other cheek when *someone else* is oppressed is not Christian behavior,” the writing reads. “It is complicity in the oppressor’s crimes.”

Mr. Trump appeared to refer to the writing in an interview on Fox News on Sunday morning when he noted that the suspect had “a manifesto” and that he “hates Christians.”

“He was a very troubled guy,” Mr. Trump said.