The rush of guests entering the White House correspondents’ dinner was over, and now Helen Mabus, a volunteer ticket checker, had a moment to herself.

“It was very quiet,” she recalled.

But just then a man out in the corridor caught her attention: He was holding what she quickly realized was a rifle. Before she could react, he tore off toward the security checkpoint about 40 feet away.

“He either unfolded a part of the gun or pieced it together,” Mabus said. “It became longer before my eyes. And within seconds, he was shooting.”

At that moment, Erin Thielman, an Air Force veteran attending the dinner at the Washington Hilton Saturday evening, was ascending the staircase leading from the ballroom entrance to the upper level where guests were screened. She was calling her son who was babysitting her other two children.

“I heard three or four really loud bangs, and I saw this man charging towards me,” she said. “He was carrying a shotgun.”

In an instant, the gunman went down, landing at Thielman’s feet.

“I didn’t even have to take a step to touch him,” she said. “I could have just bent down.”

The man was motionless, lying facedown with his hands flat on the ground and the gun beside his shoulder, Thielman said. She raced down the stairs assuming he had been shot. But officials have said that wasn’t the case — the gunman fell to the ground as the Secret Service agents he sprinted past opened fire.

“Maybe he just decided it was really a bad idea, and he was going to fall down in a defenseless position,” Thielman said. “I don’t know.”

What is clear is that the gunman — identified by authorities as Cole Allen, 31, a paying guest at the Hilton — bypassed multiple layers of security at an event attended by President Donald Trump, several top Cabinet officials and more than 2,500 journalists, politicians and other VIPs.

Allen hit the ground at the top of a staircase that led down to the entrance of the ballroom where all those guests dressed in evening wear were packed around tables awaiting an evening of lobster and speeches. The sound of gunfire set off a terrifying scramble as Secret Service and private security officers vaulted over chairs to reach the people they were charged with protecting and others hid under tables.

But no one inside the ballroom was hurt, so the Secret Service did its job, security experts say. The only injury was to a Secret Service agent who took a bullet to his vest and will survive.

Still, that an amateur gunman acting alone made it as close as he did to the president has prompted some security experts to wonder what might have happened had the attempt been carried out by more capable or determined actors.

“The thing that’s concerning is let’s say this is not this feckless hapless boob who is trying to do this,” said Jim Cavanaugh, a retired ATF agent who has worked on Secret Service details. “It’s half a dozen suicide fanatics from the Iranian Revolutionary Guard or ISIS-K, and they check in with submachine guns and hand grenades.”

“You want to have a stronger perimeter with the climate we have now,” added Cavanaugh, who is an NBC News law enforcement analyst.

The White House will hold a meeting with Secret Service and Department of Homeland Security leadership “early this week” to discuss the attempted attack and review protocols for major events, a senior White House official said Monday.

At an afternoon press conference, acting Attorney General Todd Blanche defended the actions of the Secret Service. “This man was a floor above the ballroom with hundreds of federal agents between him and the president of the United States,” Blanche said.

“Law enforcement did not fail,” he added. “They did exactly what they are trained to do.”

Thielman, the Air Force veteran who attended the dinner, said the security was standard for high-profile events. She had to show her ticket twice, then get her bag checked and go through a metal detector to enter the ballroom.

“I know they’re doing the best they can and that’s a hard situation,” she said of the Secret Service agents.

Allen was charged Monday with three counts: attempting to assassinate the president, interstate transportation of weapons and discharge of a firearm during a violent crime. He did not enter a plea.

He had checked into the Washington Hilton hotel at 3 p.m. the day before, according to an FBI affidavit, after traveling by train from Los Angeles, where he lived.

On the evening of the dinner, he used a staircase to reach the floor where guests were screened, a senior federal law enforcement official said.

At the time of his arrest, Allen had a 12-gauge pump action shotgun and a .38-caliber semiautomatic pistol, according to an FBI affidavit.

In an email he sent to his family shortly before launching the attack, Allen wrote that he was surprised at how easy it was to bring guns into a hotel where the president would be the following day.

“I walk in with multiple weapons and not a single person there considers the possibility that I could be a threat,” Allen wrote, according to a copy of the message shared with NBC News by a senior administration official. “The security at the event is all outside, focused on protesters and current arrivals, because apparently no one thought about what happens if someone checks in the day before.”

Anthony Cangelosi, a retired Secret Service agent, said his former agency would have certainly planned for that possibility, but it highlights the challenges in securing events at large multi-use buildings like hotels.

“While the Secret Service can make some alterations to the normal flow of business at a hotel during security events, there are limitations,” Cangelosi said.

The Secret Service has been under a microscope since a would-be assassin managed to fire several shots at Trump during a campaign event in Pennsylvania in 2024, injuring him and killing a rally attendee.

Robert McDonald, a retired Secret Service agent, said he thinks the agents on hand at the Washington event performed admirably, but there are still lessons to be taken away.

“Do we ever want a shooter to blow by the magnetometers like that and start peeling off rounds? Absolutely not,” said McDonald, who is now a professor at the University of New Haven. “But that’s why we’re there.”

“Once the advance is done and somebody tries to do some nefarious activity, then you have to move into a reactive fashion,” McDonald added. “That’s exactly what they did last night.”

The Washington Hilton has hosted presidential events for decades. In 1981, a would-be assassin opened fire on President Ronald Reagan outside the hotel. But he survived the attack, as did a Secret Service agent who took a bullet for the president.

The role of the Secret Service is to safeguard the specific individuals known as protectees. As a result, there was far less security at other recent White House Correspondents' Association dinners, which the president did not attend.

Some attendees of last weekend’s event were left feeling exposed after agents rushed in to evacuate the president and other top officials.

One House GOP lawmaker told NBC News they were surprised — and unsettled — by the lack of a clear security plan for the many rank-and-file members who attended the dinner.

Members of congressional leadership, who have a 24/7 protective detail from the United States Capitol Police, were evacuated from the dinner in the moments after the shooting, but other lawmakers were left locked down inside the ballroom.

Mabus, the ticket checker, said her colleagues had stepped away to eat dinner when she spotted the gunman. He was in a space outside the service elevators where hotel staff had been passing through to transport bar carts.

But at that moment, it was only him in the corridor and only her in the area where she had been checking guests’ tickets.

“There was a lull, and I think he was out of sight of security,” Mabus said. “I didn’t see how he got there.”

Mabus said she expected to be contacted by federal investigators, but as of Monday afternoon she was still waiting to hear from them.

“I think I may be the only person who was there to witness him at that moment,” she said.