WASHINGTON — A threat on Donald Trump’s life from Iran prompted additional security in the days before Saturday’s campaign rally, but it was unrelated to the assassination attempt on the Republican presidential nominee, two U.S. officials said Tuesday, as law enforcement warned of the potential for more violence inspired by the shooting.

National Security Council spokesperson Adrienne Watson said officials have been tracking Iranian threats against Trump administration officials for years, dating back to the last administration. Trump ordered the 2020 killing of Qassem Soleimani, who led the Iranian Islamic Revolutionary Guard Corps’ Quds Force.

”These threats arise from Iran’s desire to seek revenge for the killing of Qassem Soleimani. We consider this a national and homeland security matter of the highest priority,” Watson said.

The U.S. Secret Service and the Trump campaign were made aware of the latest threat, prompting a surge in resources and assets, according to the officials, who spoke on the condition of anonymity to discuss sensitive intelligence matters.

The additional resources did not prevent Saturday attack at a rally in Pennsylvania, where a 20-year-old with an AR-style rifle opened fire from a nearby rooftop, leaving the former president with an ear injury, killing one rallygoer and severely injuring two others.

Watson said there have been no ties identified between the gunman at the rally ”and any accomplice or co-conspirator, foreign or domestic.”

Since the rally shooting, rhetoric online has become particularly concerning ”given that individuals in some online communities have threatened, encouraged, or referenced acts of violence in response to the attempted assassination,” according to a joint intelligence bulletin by Homeland Security and the FBI and obtained by The Associated Press.

Presidents — and presidential candidates — are always the subject of threats, but the FBI and Homeland Security officials are “concerned about the potential for follow-on or retaliatory acts of violence following this attack,” according to the bulletin released Monday evening. Law enforcement warned that lone actors and small groups will ”continue to see rallies and campaign events as attractive targets.”

A visibly stronger security detail now surrounds Trump and President Joe Biden. And independent candidate Robert F. Kennedy Jr. received Secret Service protection in the wake of the shooting.

There were more agents surrounding Biden as he boarded Air Force One to Las Vegas on Monday night. As Trump made his first post-shooting appearance on the floor of the Republican National Convention in Milwaukee that same night, there was a much larger presence than he has previously had, with agents keeping a protective barrier between Trump and the crowd, preventing him from greeting supporters as easily as he usually does.

The visibly stepped-up presence is meant to add a show of force and additional protection, but is also an effort to reassure Americans concerned about the potential for additional violence after the already-tense and vitriolic 2024 election season turned deadly.

Both Trump and Biden have called for unity following the shooting; Biden has said repeatedly that political violence must be rejected.

The FBI has no clear motive for the shooting and the investigation is ongoing. Biden ordered an independent review of the federal response after questions swirled about how the gunman could have gotten so close to the stage, and how the enhanced security presence did not prevent the attack.

”This attack reinforces our assessment that election-related targets are under a heightened threat of attack or other types of disruptive incidents,” according to the bulletin.

Security will also be enhanced at the Democratic National Convention in Chicago in a few weeks.

The U.S. Secret Service, which is tasked with protecting the president, former presidents, their spouses, some other lawmakers and major security events, has protocols in place that allow for leeway to adjust security needs in the moment. That includes adding additional agents around the candidates, or beefing up behind-the-scenes operations and additional advance teams who travel ahead to scope out sites and test for vulnerabilities.

Federal law provides Secret Service protection to former presidents and their spouses for life. The security posture around ex-presidents varies depending on threat levels and exposure, generally being toughest in the immediate aftermath of their leaving office and getting lower-profile — but never going away — as the years go on.

Trump is the first modern ex-president to seek another term, and because of his high visibility, his protective detail has always been larger than some of his peers. That protective bubble had only grown tighter in recent months as he became the presumptive Republican presidential nominee. All major party nominees are granted enhanced security details with counterassault and countersniper teams similar to the president.

Homeland Security Secretary Alejandro Mayorkas on Monday said Biden had also ordered protection for Kennedy, whose campaign had been urging the president to provide him with Secret Service protection for months, and has sent multiple requests after various incidents.

Kennedy’s uncle, President John F. Kennedy, and his father, Sen. Robert F. Kennedy, were both assassinated.

For Trump, a stricter security protocol could hamper his interactions. He often signs autographs, shakes hands and poses for selfies on airplane tarmacs and at events.

In many cities he visits, the campaign assembles supporters in public spaces like restaurants and fast food joints. The images and video of his reception and interactions — circulated online by his campaign staffers and conservative media — have been fundamental to his 2024 campaign.

But those events can get rowdy. While he was in New York during his criminal hush money trial, Trump aides arranged a series of visits to a local bodega, a local firehouse and a construction site.

Before his arrival at the bodega in Harlem, thousands of supporters and onlookers gathered behind medical barricades for blocks to watch his motorcade arrive and cheer. But some were frustrated by the visit, including people being dropped off at a bus stop just in front of the store, and others trying to enter their apartments after work.

At one point, an individual who lived in the building started shouting from a window that was just above the entrance where Trump would eventually stand and give remarks to the cameras and answer reporters’ questions.

Biden, too, will often linger long after his events have ended, talking to people. At a campaign rally in Harrisburg, Pennsylvania, last week, he spent nearly an hour in the sun shaking hands, taking selfies and talking to people up close. Earlier in Philadelphia, he was surrounded by churchgoers as they crowded into the pews hoping to speak with him as his agents monitored the crowds and pushed people further back in some cases.

Biden often talks about how hard it is to interact with the public given security concerns.

”I love the Secret Service,” Biden said at a campaign office in Philadelphia last week. ”But I’m not able to do what I used to do.” He said he’d often be riding in a vehicle and get out to talk to people but ”realistically, I can’t do that anymore. It’s just too dangerous what’s going on out there.”

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Madhani reported from Las Vegas and Colvin from Milwaukee. Associated Press writers Zeke Miller in Washington and Jim Mustian in New York contributed to this report.