An agent fired and the gunman dropped the rifle and fled in an SUV, leaving the firearm behind along with two backpacks, a scope used for aiming and a GoPro camera, Palm Beach County Sheriff Ric Bradshaw said. The man was later stopped by law enforcement and taken into custody in a neighboring county.

He had a calm, flat demeanor and showed little emotion when he was stopped and didn't question why he was pulled over, according Martin County Sheriff William Snyder.

"He never asked, 'what is this about?' Obviously, law enforcement with long rifles, blue lights, a lot going on. He never questioned it," Snyder said.

It was the latest jarring moment in a campaign year marked by unprecedented upheaval. On July 13, Trump was shot during a rally in Butler, Pennsylvania, and a bullet grazed his ear. Eight days later, Democratic President Joe Biden withdrew from the race, giving way for Vice President Kamala Harris to become the party's nominee.

And it was sure to add to the questions about Secret Service protective operations after the agency's admitted failures in preventing the attempted assassination of Trump this summer.

In an email to supporters, Trump said: "There were gunshots in my vicinity, but before rumors start spiraling out of control, I wanted you to hear this first: I AM SAFE AND WELL!" He wrote: "Nothing will slow me down. I will NEVER SURRENDER!"

He returned to Mar-a-Lago, his private club in Palm Beach where he lives, according to a person familiar with Trump's movements who was not authorized to discuss them publicly and spoke on condition of anonymity.

It was not immediately clear whether the incident would affect his campaign schedule. He was set to speak from Florida about cryptocurrency live on Monday night on the social media site X for the launch of his sons' crypto platform. He planned a town hall Tuesday in Flint, Michigan, with his former press secretary, Arkansas Gov. Sarah Huckabee Sanders, followed by a rally Wednesday on New York's Long Island.

An email to Trump campaign staffers obtained by AP said, "This is not a matter that we take lightly. Your safety is always our top priority. We ask that you remain vigilant in your daily comings and goings."

"As we enter the last 50 days of President Trump's campaign, we must remember that we will only be able save America from those who seek to destroy it by working together as one team."

Biden and Harris were briefed and would be kept updated on the investigation. The White House said they were "relieved" to know Trump is safe.

Harris, in a statement, also said "violence has no place in America."

In the aftermath, Trump checked in with allies, including running mate Ohio Sen. JD Vance, South Carolina Sen. Lindsey Graham and several Fox News hosts.

Fox News host Sean Hannity recounted on air his conversation with Trump and the former president's golf partner, Steve Witkoff.

They told Hannity they had been on the fifth hole and about to go up to putt when they heard a "pop pop, pop pop." Within seconds, he said Witkoff recounted, Secret Service agents "pounced on" Trump and "covered him" to protect him.

Trump had returned to Florida this weekend from a West Coast swing that included a Friday night rally in Las Vegas and a Utah fundraiser. His campaign had not advised about any public plans for Trump on Sunday. He often spends the morning playing golf, before having lunch at the club, one of three he owns in the state.

He has had a stepped-up security footprint since the assassination attempt in July. When he has been at Trump Tower in New York, parked dump trucks have formed a wall outside the building. At outdoor rallies, he now speaks from behind an enclosure of bulletproof glass.

The Florida golf course was partially shut down for Trump as he played, but there are several areas around the perimeter of the property where golfers are visible from the fence line. Secret Service agents and officers in golf carts and on ATVs generally secure the area several holes ahead and behind Trump when he plays. Agents also usually bring an armored vehicle onto the course to shelter Trump quickly should a threat arise.

The Palm Beach County sheriff said the entire golf course would have been lined with law enforcement if Trump were the president, but because he is not, "security is limited to the areas that the Secret Service deems possible."

"I would imagine that the next time he comes to the golf course, there will probably be a little more people around the perimeter," Bradshaw said. "But the Secret Service did exactly what they should have done, they provided exactly what the protection should have been and their agent did a fantastic job."

Former presidents and their spouses have Secret Service protection for life, but the security around former presidents varies according to threat levels and exposure, with the toughest typically being in the immediate aftermath of their leaving office.

Trump's protective detail has been higher than some other former presidents because of his high visibility and his campaign to seek the White House again.

The man in custody was Ryan Routh, three law enforcement officials told the AP. The officials who identified the suspect spoke on the condition of anonymity because they were not authorized to discuss the ongoing investigation.

The FBI was leading the investigation and was working to determine any motive. Attorney General Merrick Garland was receiving regular updates. Agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives were helping investigate.

"The FBI has responded to West Palm Beach Florida and is investigating what appears to be an attempted assassination of former President Trump," the bureau said.

News reporters were not with Trump on Sunday. Bucking tradition, Trump's campaign has not arranged to have a protective pool of reporters travel with him, as is standard for major party nominees and for the president. Harris does not have a protective pool at all times, but does allow reporters to travel with her for public events.

Snyder, the Martin County sheriff, said the suspect was apprehended within minutes of the FBI, Secret Service and Palm Beach County Sheriff's Office putting out a "very urgent BOLO" — or "be on the lookout" alert detailing the specific vehicle sought, license plate number and description of the occupant.

Snyder said his deputies "immediately flooded" northbound I-95, deploying to every exit between the Palm Beach County line to the south and St. Lucie County line to the north.

"One of my road patrol units saw the vehicle, matched the tag and we set up on the vehicle," Snyder said, "We pinched in on the car, got it safely stopped and got the driver in custody."