A second apparent assassination attempt on former President Donald Trump — this time as he played golf in Florida — has rocked a presidential campaign already marred by unprecedented violence and raised questions about how such a thing could have happened for the second time in as many months.

U.S. Secret Service agents opened fire Sunday afternoon on a man who was spotted pointing an AK-style rifle through a fence while hiding in the bushes as Trump golfed at his club in West Palm Beach. The FBI described it as an apparent attempted assassination on the GOP nominee.

At a Pennsylvania rally in July, Trump was grazed in the ear by a bullet when a gunman was able to gain access to an unsecured roof, unleashing a hail of bullets that left one of Trump's supporters dead and two others badly injured.

While the Secret Service has grappled with how to keep Trump safe as he campaigns across the country, holding rallies that often draw thousands, less attention has focused on his protection when he is off the trail, often at his own clubs and properties.

The fact that there are places along the perimeter of the property where golfers — including Trump — are visible to those standing behind the fence has long been known to law enforcement. While Trump was president, news photographers were often able to capture images of him on the greens by finding gaps in the shrubbery.

While Trump's plans to golf Sunday were not part of any public schedule, on days he is not campaigning, he can often be found golfing at one of his courses. Trump International Golf Club, West Palm Beach, about a 10-minute drive from his Mar-a-Lago residence, is a favorite. One of three golf clubs he owns in Florida, it boasts 27 holes of championship golf, as well as event spaces. Trump often eats lunch and holds meetings in the clubhouse between rounds.

Trump had just returned from a West Coast swing that included stops in Las Vegas and Utah, and had announced on social media that he would be delivering remarks Monday from Mar-a-Lago about cryptocurrency as he launches a new crypto platform.

Palm Beach County Sheriff Ric Bradshaw noted at a briefing that because Trump is no longer in office, security protocols around the course had loosened.

“He's not the sitting president. If he was, we would have had this entire golf course surrounded. But because he's not, his security is limited to the areas that the Secret Service deems possible," he told reporters.

Law enforcement officials praised the work of the agents assigned to protect Trump. One agent, tasked with jumping one hole ahead of the former president to scope out potential threats, managed to spot the gunman's rifle barrel sticking out of the fence that surrounds the golf club and “immediately engaged that individual,” Bradshaw said.

In an email to campaign staff Sunday night, senior campaign advisers Chris LaCivita and Susie Wiles credited the Secret Service for saving Trump, who has praised the agents in his own protective detail for their bravery as they rushed on stage to protect him in Butler, Pennsylvania.

"President Trump and everyone accompanying him are safe thanks to the great work of the United States Secret Service,” they wrote.

Unlike other past presidents and typical VIPs who live in private residences with tall fences or in gated communities, Trump has his official residence at his Mar-a-Lago club in Palm Beach. The club is open to dues-paying members, who mingle with the former president at meals and at events and can invite their own guests to the property.

Many nights, Trump holds court on the club's patio, playing DJ with his iPad. While president, he once plotted a response to a North Korean missile launch from the candlelit terrace, the meeting captured and posted on social media by a club member.

The club is also a popular Palm Beach venue and hosts a constant stream of fundraisers, weddings and other events that sometimes see Trump drop by unannounced.

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

The incident sparked immediate finger-pointing and calls for answers from Trump's allies on Capitol Hill.

New York Rep. Elise Stefanik, the House Republican Conference chair and a close ally of the former president, said she was grateful Trump was safe. “However, we must ask ourselves how an assassin was allowed to get this close to President Trump again?”

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 Rep. Mike Kelly, R-Pa., and Rep. Jason Crow, D-Colo., in a joint statement.

Meanwhile, Florida Gov. Ron DeSantis, one of Trump's rivals in the GOP primary, 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.

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