Donald Trump’s suspected would-be assassin has been charged with two gun-related crimes as body cam footage emerged of the “perplexing” moments he was arrested.

A smiling and laughing Ryan Wesley Routh, 58, appeared in federal court a day after allegedly being spotted with a rifle hiding in the bushes at the former US president’s golf course in West Palm Beach, Florida.

Routh may have been lying in wait for nearly 12 hours before Trump turned up to play golf on Sunday (US time), according to a criminal complaint.

More charges appear likely, but the initial counts – possessing a firearm as a convicted felon and possessing a firearm with an obliterated serial number – will allow authorities to keep him in custody as the investigation continues.

The FBI is investigating the incident as a suspected assassination attempt on the Republican presidential candidate.

Police body cam footage from the arrest reveals Routh’s unusually calm demeanour when he was pulled over by the sheriff’s deputies on Florida’s interstate highway after fleeing the golf club on Sunday (local time).

Routh’s shirt is lifted and he walks backwards, as ordered by police. Photo: Martin Country Sheriff’s Office 

Routh, dressed in long pants and a pale salmon-coloured shirt, is surrounded by deputies with rifles who shout orders.

He walks backwards with his shirt pulled over his head, exposing his back, before he is cuffed and taken into custody.

Martin County Sheriff William Snyder told CNN Routh’s behaviour could be described as “perplexing” during the stop.

“His facial affect was so flat. His demeanour was relaxed I honestly thought it looked like somebody that just left the church picnic and was on his way home,” he said.

Ryan Routh’s demeanour is described as ‘perplexing’. Photo: Martin Country Sheriff’s Office 

The incident raised fresh questions about how an armed suspect was able to get so close to Trump, just two months after another assassination attempt on July 13 at a rally in Pennsylvania.

Meanwhile, Trump posted an explosive rant on Tuesday (AEST), blaming President Joe Biden and his election rival, Vice-President Kamala Harris, for taking politics “to a whole new level of Hatred, Abuse, and Distrust”.

“The bullets are flying, and it will only get worse!” he posted on X.

Trump also used the moment to push more anti-immigrant rhetoric in capital letters.

“Allowing millions of people, from places unknown, to INVADE and take over our Country, is an unpardonable sin OUR BORDERS MUST BE CLOSED, AND THE TERRORISTS, CRIMINALS, AND MENTALLY INSANE, IMMEDIATELY REMOVED FROM AMERICAN CITIES AND TOWNS, DEPORTED BACK TO THEIR COUNTIES OF ORIGIN.”

Earlier, Trump told Fox News that Biden and Harris were to blame for the assassination attempt.

He cited their “rhetoric” and claimed the suspected gunman was acting on Democrats’ “highly inflammatory language”. Authorities have not yet offered evidence of any motive.

“Their rhetoric is causing me to be shot at, when I am the one who is going to save the country, and they are the ones that are destroying the country – both from the inside and out,” he said, according to Fox.

The US Secret Service foiled the suspected assassination attempt after an agent spotted a rifle barrel poking out of the bushes at Trump’s Florida golf course.

Routh was a few hundred metres from Trump, as he played a round with a key donor.

The Secret Service opened fire and the gunman fled in a sports utility vehicle, according to the complaint. Police say he left behind a loaded assault-style rifle with scope, a digital camera and a plastic bag of food.

Routh was arrested about 40 minutes later driving north on Interstate 95.

When asked if he knew why he had been stopped, Routh “responded in the affirmative”, according to the complaint. The licence plate on his vehicle had been reported stolen from another car.

Records show a phone associated with Routh was found at the golf course.

Routh has two prior convictions, both in North Carolina. According to the criminal complaint, they are a 2002 conviction for possessing a weapon of mass death and destruction and a 2010 conviction for possessing stolen goods. Further details about those cases were not immediately available.

The Secret Service, which protects US presidents, presidential candidates and other high-level dignitaries, has been under intense scrutiny since the earlier attempt on Trump’s life.

The agency “needs more help,” including possibly more personnel, Biden said on Monday, adding “Thank God [Trump’s] OK”.

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

Routh was a staunch supporter of Ukraine and had travelled there after Russia’s 2022 invasion, seeking to recruit foreign fighters.

Profiles on X, Facebook and LinkedIn with Routh’s name included messages of support for Ukraine, as well as statements describing Trump as a threat to US democracy.

“Your campaign should be called something like KADAF Keep America democratic and free; Trumps should be MASA make Americans slaves again master DEMOCRACY is on the ballot and we cannot lose,” read one post on X, tagging Biden.

Public access to the Facebook and X profiles was removed hours after Sunday’s incident.

-with AAP