A picture is emerging of the suspect in a shooting incident at the hotel where the White House Correspondents' Association dinner was being held on Saturday night.
Cole Tomas Allen, 31, appeared in court on Monday charged with attempting to assassinate US President Donald Trump and two firearms offences.
Jeanine Pirro, US attorney for Washington, told a news conference that additional charges could be filed.
The suspect, who described himself as a mechanical engineer, game developer and teacher, is from the Los Angeles suburb of Torrance.
He is due to return to court on Thursday to determine whether he will remain in custody.
The suspect is also charged with using a firearm during a crime of violence and interstate transportation of a firearm with intent to commit a felony.
During Monday's news conference, Pirro cited an email the suspect allegedly sent to his family and a former employer shortly before gunfire rang out at the Trump event.
According to an affidavit, the accused wrote to his relatives, "Administration officials... are targets, prioritized from highest-ranking to lowest".
He allegedly referred to himself as "Friendly Federal Assassin' Allen" in the email, whose attachment was titled "Apology and Explanation".
During Monday's news conference, acting US Attorney General Todd Blanche set out the alleged timeline.
On 21 April, the suspect left his home in the Los Angeles area by train, travelling to Chicago, Blanche said.
On 24 April, the eve of the dinner, he left Chicago and arrived in Washington DC. He checked into the Washington Hilton hotel and stayed overnight.
On 25 April, he approached a security checkpoint at the event, and "ran through while holding a long gun", according to Blanche.
Secret Service then "heard a loud gunshot", Blanche said, adding that one agent "was shot in the chest but wore a ballistic vest which worked". It is not clear who shot the agent.
The weapon allegedly discharged by the suspect was a shotgun, Blanche said.
The accused sustained no injuries other than a scrape to his knee, according to Pirro.
Police said the suspect had exchanged fire with security agents on a level of the Washington Hilton that was one floor above the room in which Trump had gathered with members of his cabinet and hundreds of journalists and other guests.
After he was detained, Allen told officials he wanted to shoot officials in the Republican president's administration, two sources told CBS, the BBC's US partner.
Federal campaign finance records show the suspect donated $25 to a Democratic Party political action committee in support of Kamala Harris for president in 2024.
US media reported a history of anti-Trump social media posts from the accused, citing law enforcement sources.
BBC Verify has been looking into social media accounts with the same username reportedly used to sign the email that was allegedly sent by the suspect to family members.
In January the account posted on the social network Bluesky: "The country will continue to crash and burn until people stop asking when other people will step up."
In April the account posted that Trump was a "villain" and a "desperate man".
Resharing a video of Vice-President JD Vance saying that stopping funding for the war in Ukraine was one of his proudest achievements, the user wrote "he's proud that we don't uphold our commitments", before using an expletive.
A Bluesky post earlier this month criticised plans by some journalists to wear white pocket squares at the White House media gala, to promote press freedom, calling them "pathetic".
On Sunday, Trump told Fox News that the suspect "had a lot of hatred in his heart for a while".
The suspect's usually quiet neighbourhood of Torrance was swarming with media a day after the shooting.
Local residents seemed shocked. They thought he lived in the house with his parents - many said they waved to him regularly but did not know him well.
Some of them pointed out that the garage's windows appear to be covered, which they had not noticed before.
On LinkedIn, the defendant described himself as a mechanical engineer, game developer and teacher.
According to his profile, he studied mechanical engineering at the California Institute of Technology (Caltech), a highly competitive university, where he took part in its Christian fellowship.
He worshipped at the Pasadena United Reformed Church in the Los Angeles area, its pastor told the BBC.
The accused graduated with a masters in computer science in 2025 from California State University, Dominguez Hills, and shared a photo of himself in graduation robes to LinkedIn.
Bin Tang, a professor in the computer science department at Cal State, told CBS that the suspect was an exemplary student.
"He was a very good student indeed, always sitting in the first row of my class, paying attention, and frequently emailing me with coursework questions," Tang said, adding that the accused was "soft spoken, very polite, a good fellow".
"I am very shocked to see the news," the professor added.
The defendant also developed and released a game called "Bohrdom" to the gaming platform Steam.
On Facebook, photos of Allen - which BBC Verify has matched to those of his arrest at the Washington Hilton - show him smiling in family pictures at Christmas and graduation events.
In December 2024, he was named teacher of the month by C2 Education, which offers tutoring and college test preparation to students, according to the organisation's Facebook post.
He has been a part-time teacher there since 2020, his LinkedIn profile says.
The Torrance Unified School District told CBS in a statement that Allen has never been an employee of their district.
Additional reporting by Regan Morris in Los Angeles
