Investigators said the gunman who tried to storm a gala dinner attended by Donald Trump planned to assassinate the US president and multiple top officials, as scrutiny grew over the event's security.Trump, who was rushed out of the hotel ballroom in Washington by Secret Service agents, posted surveillance footage of the gunman attempting to sprint past a checkpoint.After a brief exchange of gunfire with agents, the suspect was detained at the scene on Sunday AEST and was being questioned before he is due to appear in court on Monday.Trump shared photos of the suspect handcuffed on the carpeted hotel floor."He's not actively cooperating They were even complaining to law enforcement.""When you read his manifesto, he hates Christians," Trump said.The New York Post said the suspect, widely named as Cole Allen, 31, had written in a note shared with his family shortly before the attack that his targets would be "prioritised from highest-ranking to lowest."In the seconds after the shooting on a floor above, Secret Service agents swarmed into the ballroom, prompting chaotic scenes as attendees dove under tables.Crowded into the ballroom were Trump, first lady Melania Trump, vice president JD Vance, several cabinet members and top politicians, and hundreds of guests in black tie.Trump said at a hastily arranged late-night news conference at the White House that he first thought the noise was a tray being dropped, before realising it was gunfire.He said he hoped the annual gala, hosted by the White House Correspondents' Association, would be rescheduled within a month."They seem to think he was a lone wolf, and I feel that too," the president said