Trump shooting updates: Shooter flew drone near site hours before shooting

The shooting at the Trump rally is officially being investigated as an assassination plot on Trump, a senior defense official told ABC News.

Early evidence indicates that there was only one shooter, according to the source.

Attorney General Merrick Garland said in a statement that the FBI; Bureau of Alcohol, Tobacco, Firearms and Explosives; U.S. Attorney’s Office for the Western District of Pennsylvania; and the Department’s National Security Division will be involved in the investigation.

"My heart is with the former President, those injured, and the family of the spectator killed in this horrific attack," he said in a statement. "We will not tolerate violence of any kind, and violence like this is an attack on our democracy. The Justice Department will bring every available resource to bear to this investigation."

-ABC News' Pierre Thomas

The Trump campaign released a statement indicating the former president will be attending the Republican National Convention in Milwaukee next week.

"As was communicated earlier this evening, President Trump is doing well and grateful to law enforcement and first responders for their fast action," the campaign said.

"President Trump looks forward to joining you all in Milwaukee as we proceed with our convention to nominate him to serve as the 47th President of the United States," they added.

-ABC News' Lalee Ibssa

Trump's son Eric told ABC News that his father is the "toughest man I have ever met" without elaborating on the former president’s condition.

-ABC News' John Santucci

Ivanka Trump released a statement on X thanking supporters for their thoughts and prayers for her father and the victims of the shooting.

"I am grateful to the Secret Service and all the other law enforcement officers for their quick and decisive actions today. I continue to pray for our country. I love you Dad, today and always," she said.