The FBI is investigating what it has described as an attempted assassination of Donald Trump after Secret Service agents spotted the muzzle of a rifle poking through a fence close to where the former US president was playing golf at his club in Florida. A suspect has been arrested and an assault rifle was recovered at the course.

The incident occurred at the Trump International Golf Club in West Palm Beach.

At about 1.30pm local time (18.30 BST) on Sunday, Secret Service agents spotted a gun barrel and opened fire at the suspect, who fled and escaped in a car up the Interstate 95 (I95) highway.

A few hundred metres away, Trump and his golf partner, Steve Witkoff, a real estate investor, were on the fifth hole and about to putt when they heard the “pop, pop, pop, pop” of gunfire, according to Sean Hannity, a Fox News host and Trump’s friend.

Secret Service agents immediately used their bodies to shield Trump and moved him to the golf course’s clubhouse, where he remained until he went back to his Mar-a-Lago resort home about 15 minutes away.

An “AK-47-style” rifle with a scope, two backpacks containing “ceramic tiles” and a GoPro camera were found at the scene and were believed to have been left by the alleged shooter, police said.

A witness saw the alleged gunman leaving the scene and managed to take photos of his car, a black Nissan, including the licence plate.

In a press conference, the Palm Beach county sheriff, Ric Bradshaw, said a male suspect was later stopped on the I95 and detained by authorities. According to Bradshaw, the suspect was relatively calm.

Overnight, images emerged of Secret Service and homeland security agents searching the suspect’s former home in Greensboro, North Carolina, almost 800 miles (1,300km) north of the Florida golf club.

Law enforcement officials have not officially named a suspect or given any immediate indication of a motive.

However, a source with direct knowledge of the investigation told the Guardian that the man is Ryan Wesley Routh, 58, who has previously travelled to Ukraine and sought to recruit overseas fighters to support Kyiv in its war.

Routh appeared in court on Monday and was charged with two gun-related crimes – possessing a firearm despite being a convicted felon, and possessing a firearm with an obliterated serial number – in what is likely to be an initial move to allow authorities to keep him detained while they work on the case.

In an email to supporters after the incident, 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 added: “Nothing will slow me down. I will NEVER SURRENDER!”.

The Republican vice-presidential candidate, JD Vance, said he spoke to Trump after the shooting and that the former president was in good spirits.

Trump was previously injured in an assassination attempt in Pennsylvania on 13 July, which killed a spectator. The shooter in that attempt was killed by security agents.