What is the ‘perimeter’ for presidential security?

(CNN) — Video from Saturday shows an armed man racing through a security checkpoint at the Washington Hilton, one floor above the ballroom where President Donald Trump, top administration officials and journalists were attending the White House Correspondents’ Dinner. Hotel security footage captured Secret Service officers drawing their weapons moments later, and a subsequent clip indicates that the intruder was captured before reaching a staircase leading down to the event.

“It was a massive security success story,” Acting Attorney General Todd Blanche said on CNN’s “State of the Union.” “If you think about what happened, as far as what we know right now, this suspect barely breached the perimeter.”

Despite the disruption and the shock to the attendees, to judge by the outcome, the protective measures worked. The alleged would-be assassin never made it to the ballroom where the dinner was happening. The president and vice president were quickly rushed to safety. The one person hit by gunfire was a Secret Service officer wearing a bulletproof vest, who Trump told reporters was okay after a brief hospitalization. No one died.

But the fact that anyone breached the “perimeter” even slightly has led to a new round of complaints and questions about the bounds of presidential protection: Did the “perimeter” at the Correspondents’ Dinner extend far enough? Would a wider “perimeter” amount to tighter security? Can a “perimeter” at a venue open to the general public be truly secure?

“Perimeter,” from the Latin “perimetros” via ancient Greek, seems to have entered English around the 15th century, appearing in a Middle English translation of Guy de Chauliac’s seminal surgical guide “La Grande Chirurgie.” The word refers to a line delineating the boundary of a closed geometrical figure or of a particular area; over time, “perimeter” also came to encompass figurative boundaries, as in teenagers testing the perimeters of their independence. It has since acquired additional applications: In basketball, the NBA’s statistics glossary defines defense on the “perimeter” as happening “more than 20 feet from the basket;” in ophthalmology, it’s an instrument that measures a patient’s field of vision.

In presidential security parlance, the “perimeter” is a protective barrier guarded by the Secret Service that secures the area around the commander-in-chief. But the boundary separating the president from the general public is more fluid than the word suggests — the perimeter can expand or contract depending on the particulars of the event, the location and the people requiring access to the president at a given time, says Robert McDonald, who worked for the Secret Service spanning the presidential administrations of Bill Clinton, George W. Bush and Barack Obama.

The Hilton may have been the venue for the event, but that doesn’t mean the hotel itself counted as a perimeter. “When we say a hard perimeter, I’m not sure that’s a fair definition with respect to this venue and this event, with this size ballroom,” McDonald says. “The secure perimeter is basically the inside there. And then there are other rings of security, but with a lot more porousness. It’s not like there’s a chain link fence for four blocks around the venue.”

The physical considerations of a space play a big role in setting the perimeter, says Bill Gage, who spent 12 years as a Secret Service special agent. The Washington Hilton is first and foremost a hotel, with regular guests continuing to come and go while the Correspondents’ Dinner takes place. In these cases, Gage says the Secret Service tries to minimize disruptions to routine business operations to whatever extent possible while securing the area around the president.

Presidential security consists of multiple layers of protection, which are generally referred to as the outer perimeter, middle perimeter and inner perimeter, Gage explains. The outer perimeter is a first line of defense, typically marked by some sort of security checkpoint. In this instance, the magnetometer machines screening event attendees inside the hotel formed the outer perimeter, and the ballroom formed the middle perimeter. Inside the ballroom, a tightly controlled area around the president formed the inner perimeter.

Each of these perimeters is designed to overlap and interlock with another, says Gage — if someone is able to breach one layer, the next layer should theoretically subdue a potential attacker before they can reach the president. “Before they penetrate that inner perimeter, they would have had to go through so many layers of security that they’re going to get delayed, delayed, delayed, and by that point, either arrested or eliminated,” he says.

Where each of these perimeters begin and end can be fuzzy to the general observer. Tomas Allen, the 31-year-old man facing criminal charges in the incident, reportedly expressed surprise at what he perceived as lax security at the venue. “Like, I expected security cameras at every bend, bugged hotel rooms, armed agents every 10 feet, metal detectors out the wazoo,” he allegedly wrote in a note to family members before the attack. “What I got (who knows, maybe they’re pranking me!) is nothing.” What the note was describing lay outside the perimeter.

Though the perimeter did hold for the most part, lawmakers and law enforcement experts expressed concerns about why it didn’t extend further, as well as about Secret Service staffing shortages and personnel burnout, CNN reported on Wednesday. One source familiar with Secret Service operations said pushing the perimeter further away from the ballroom would have required additional staffing at a time when the agency was already stretched thin. Secret Service Director Sean Curran was recently asked the same question by reporters, saying, “There’s a reason, but I’m not going to get into that. It’s classified. I don’t want to get into why we do that, but there’s a reason.”

McDonald says the answers to those questions should come as the result of an investigation.

“If the perimeter gets knocked out another 25 or 30 or 40 feet or 40 yards and this happens again, well then the answer is it really didn’t matter at that point,” he says. “But I think you’re going to see perimeters farther out — if possible, again, with the physicality of venues — to make sure that something like this gives the agents and officers a little bit more time to react.”

Saturday’s incident is likely to spur new conversations about the “perimeter” and security for future events. Joseph Petro, who served as a Secret Service agent for more than two decades, says it also raises questions about whether a hotel, a venue open to the general public, can be adequately protected. To that end, Trump and his allies have seized the opportunity to push for the construction of his proposed ballroom, which is currently caught up in legal proceedings. “When the White House ballroom is complete, President Trump and his successors will no longer need to venture beyond the safety of the White House perimeter to attend large gatherings at the Washington Hilton ballroom,” Assistant Attorney General Brett Shumate wrote in a letter dated a day after the incident.

People have breached the “perimeter” before, prompting similar conversations about presidential security. Forty-five years ago, President Ronald Reagan faced an assassination attempt at the same hotel. The attack — which seriously wounded the president, White House press secretary James Brady, Secret Service agent Tim McCarthy and DC police officer Thomas Delahanty — led to the implementation of heightened security measures at the hotel and beyond. The Hilton built an enclosed garage after the fact to allow the president to enter the hotel more securely. Petro, who joined Reagan’s security detail soon after the attempt, says that in other instances, the agency began erecting tents leading from the outside of a venue into the entrance. “We just eliminated any potential vantage point from outside the perimeter,” he says.

In more recent history, in 2014, a man jumped the White House fence and made it all the way across the grounds, inside the building and into the East Room before the Secret Service managed to stop him. President Obama was not in the building during the incident, and afterward a second fence was set up outside the regular one.

In February of this year, Secret Service agents and law enforcement shot and killed a man who entered the perimeter around Trump’s Florida estate. In 2024, Secret Service fired on a suspect after spotting him in the bushes of Trump International Golf Club in Florida. And a few months before that, at a campaign rally in Butler, Pennsylvania, a gunman climbed onto the roof of a nearby building and attempted to shoot the president.

CNN’s Jeremy Herb, Jamie Gangel, Whitney Wild, Josh Campbell and Betsy Klein contributed to this report.

The-CNN-Wire
™ & © 2026 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.