Another assassination attempt on Donald Trump — this time as he played golf at one of his resorts in Florida —has prompted questions about safety, security, and how an attempt on the life of a US presidential candidate was almost  allowed to occur again.

US Secret Service agents opened fire on Sunday afternoon on a man who was spotted pointing an AK-style rifle through a fence while hiding in the bushes as Mr Trump golfed at his club in West Palm Beach.

Secret Service spokesperson Anthony Guglielmi said in a social media post that the agency is now working closely with the FBI, Palm Beach County Sheriff’s Office and other law enforcement to investigate what happened.

Mr Trump will be briefed in person Monday by acting Secret Service director Ronald Rowe about the investigation, a person familiar with the plan told the Associated Press, however, the source was not authorised to speak publicly on the matter.

The incident sparked immediate finger-pointing and calls for answers on Capitol Hill.

New York representative and close ally of the former president, Elise Stefanik, said she was grateful Mr Trump was safe.

“However, we must ask ourselves how an assassin was allowed to get this close to President Trump again?” she asked in a statement.

The leaders of the bipartisan task force that has been investigating the security failures in Pennsylvania said they were monitoring the situation and had requested a briefing from the Secret Service.

“We are thankful that the former President was not harmed, but remain deeply concerned about political violence and condemn it in all of its forms,” said representatives Mike Kelly and Jason Crow in a joint statement.

Meanwhile, Florida governor Ron DeSantis said his state will conduct its own investigation.

“The people deserve the truth about the would-be assassin and how he was able to get within 500 yards of the former president and current GOP nominee,” he wrote in a social media post.

Democratic representative Ro Khanna echoed that message.

“Two assassination attempts in 60 days on a former President & the Republican nominee is unacceptable,” he wrote.

“The Secret Service must come to Congress tomorrow, tell us what resources are needed to expand the protective perimeter, & lets allocate it in a bipartisan vote the same day.”

President Joe Biden said in a statement that he was “relieved” that Mr Trump was unharmed and  that “there is no place for political violence or for any violence ever in our country”.

The US President added he had directed his staff “to continue to ensure that Secret Service has every resource, capability and protective measure necessary to ensure the former president’s continued safety”.

Mr Trump was also the target of an assassination attempt in July when he was grazed in the ear by a bullet at an election rally in Pennsylvania.

A gunman was able to gain access to an unsecured roof and unleashed a slew of bullets at the Republican nominee, killing one of Mr Trump’s supporters and leaving two others injured.