The Washington Hilton hotel was attacked on Sunday night during a banquet for White House journalists attended by US President Donald Trump, his wife, and administration officials.
Secret Service agents subdued and detained the gunman. One agent was wounded.
Trump said he left the hotel for his safety. An investigation has been launched.
The president suggested the attacker acted alone and dismissed any connection to the situation in Iran or foreign policy, but suggested the attack reflected his political impact.
"They're trying to kill the presidents who have the most influence on the country",
Trump said.
According to media reports, the suspect is 31-year-old Cole Thomas Allen of California. He had previously stayed at the Washington Hilton, and several weapons were found on him. Investigators are working to determine the motive and details of the attack.
Forensic teams remain at the scene, and the hotel has been sealed off. The cancelled gala has been rescheduled for a later date.
