The suspect behind the second apparent attempted assassination of former US president Donald Trump has been identified.

US media is reporting that 58-year-old Ryan Wesley Routh of Hawaii is the man in custody after the incident at Trump’s golf course in West Palm Beach, Florida, on Sunday afternoon (US time).

The New York Times and Fox News Channel were among those to identify Routh, citing law unnamed enforcement officials.

Numerous photos of a man said to be Routh are being shared online. They show him wearing American flag-style clothing and outside the US Capitol in Washington DC.

Photos said to be of would-be Trump shooter Ryan Routh are circulating online.

Authorities have said the suspected gunman was spotted near the property line of the golf course after Secret Service agents, who were clearing holes ahead of where Trump was playing, saw a rifle barrel sticking through the chainlink fence.

Agents engaged the gunman and fired at least four rounds of ammunition about 1.30pm.

The gunman dropped his rifle, two backpacks and other items and fled in a black Nissan.

“We are able to catch a witness that came to us and said, ‘Hey, I saw the guy running out of the bushes, he jumped into a black Nissan and I took a picture of the vehicle and the tag’, which was great,” Palm Beach County Sheriff Ric Bradshaw said.

The gunman was spotted about 350-450 metres from where Trump was playing, Bradshaw said, adding: “The Secret Service did exactly what should have been done.”

Authorities sent out a statewide alert on the vehicle, which led to sheriff’s deputies in neighbouring Martin County apprehending the suspect an interstate highway.

Martin County Sheriff William D. Snyder told local media the driver was “relatively calm” and “not displaying a lot of emotions.”

“We have somebody in custody right now that is a potential suspect. In the bushes, where this guy was, is an AK-47-style rifle with a scope,” Bradshaw said.

He said investigators also found two backpacks filled with ceramic tile, and a GoPro camera hanging on a fence at the golf course.

Bradshaw said the would-be shooter was apparently “intent on filming what was going on”, although he did not reveal any possible motive.

Police found an AK-47 rifle, backpack and Go-Pro camera on a fence outside the golf course. Photo: AAP

The FBI said it was “investigating what appears to be an attempted assassination” of Trump.

Trump’s campaign had earlier said he was safe following gunshots in his vicinity.

Trump sent an email to his fundraising list saying there were “gunshots in my vicinity, but before rumours start spiralling out of control, I wanted you to hear this first: I AM SAFE AND WELL!” according to an email seen by Reuters.

He also spoke to Fox News, revealing he was playing the fifth hole when shots rang out. Trump said there was no evidence any shots were near him.

He was put in a golf cart and driven back to the clubhouse.

“Tell everybody I am fine and the Secret Service did a great job,” he said.

It came just two months after Trump was injured in an assassination attempt in Pennsylvania on July 13, raising questions about protection for candidates just months ahead of the highly contested November 5 election between him and Democratic Vice President Kamala Harris.

The White House said in a statement that President Joe Biden and Harris had been briefed about the incident and were relieved to know that Trump was safe.

“Violence has no place in America,” Harris said on X.

Trump’s running mate in the presidential election, US Senator JD Vance, said he spoke to Trump after the shooting and that the former president was in good spirits.

The Pennsylvania incident – the first shooting of a US president or major party presidential candidate in more than four decades – was a glaring security lapse that forced Kimberly Cheatle to resign as Secret Service director under bipartisan congressional pressure.

Trump was grazed in the right ear and one rallygoer was killed in the gunfire. The gunman, identified as a 20-year-old Thomas Crooks, was shot and killed by a Secret Service sniper.

The US Secret Service’s new acting director, Ronald Rowe, said in August that he was “ashamed” of a security lapse that led to the assassination attempt.

He was reportedly on his way to Florida after Sunday’s incident.

-with AAP