She knew something was wrong when he sat near her kids. He was removed from the flight.

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Lauren Benton said something seemed wrong the moment she left the Transportation Security Administration checkpoint on the way to her flight.

She and her husband Nathan, and their two kids, ages 9 and 6, were flying home to Georgia on Delta Air Lines from Washington Dulles International Airport on Aug. 2. Benton said a man who was near her family at the checkpoint started following them to their gate. At one point, she said the man even went into the women’s restroom while Benton was there with her daughter.

“My heart sunk down into my stomach,” Benton told USA TODAY. “With our children we were trying to create the perception that they were safe at all times.”

Benton said the man continued to follow them even when her family got on the plane during early boarding and sat down in their row. At that point, she knew she needed to say something as her kids became more anxious. She called over a flight attendant and discreetly informed them of the situation.

Ultimately, the man was escorted off the plane. He did not have a boarding pass for the flight Benton was on with her family, but he did have a boarding pass and valid identification for another flight that day.

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Because the man was not ticketed for the Delta flight, the plane had to be evacuated and a security sweep was conducted, which Benton said took about an hour and a half or two hours.

The TSA, Metropolitan Washington Airports Authority, which operates Dulles Airport, and Delta all acknowledged the incident in separate statements.

TSA told Benton it was investigating the incident, but in a statement to USA TODAY said there were no lapses at the checkpoint since the man had a valid boarding pass and ID.

MWAA acknowledged that the man was escorted off the plane, but said no charges were filed and he ultimately continued on to his original destination.

Delta also said it is investigating the incident, since the man was able to board one of its planes without a valid boarding pass for that flight.

“Delta has processes in place for gate agents and flight crews to verify that individuals onboard aircraft prior to departure are customers that are booked on that particular flight. Delta is reviewing the matter in question internally and has been in touch with airport authorities in conjunction with this review,” its statement said.

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For Benton, she said she doesn’t understand how the lapse could have happened in the first place.

“Individuals that belong on the plane should only have been allowed on the plane. I would like to know how this occurred,” she said. “We live in this post 9/11 era and people think something like this is not possible and it’s completely possible.”

Authorities said the man who followed Benton appeared to have mental health issues. Benton said she sympathizes with her fellow traveler’s struggles but added that it can’t be an excuse for this kind of security lapse.

“I have empathy toward the mental health crisis that we have in the United States, but I will not allow mental health to be used as an excuse for the (compromising) of my family’s safety,” Benton said. She also acknowledged that she and her husband could have escalated their concerns to airport authorities sooner, but they were trying to remain calm to not upset their children.

Benton said she hopes the stakeholders in this situation will work harder to prevent similar lapses in the future, but in the meantime, she said she and her family will develop their own safety plan.

“Just don’t be complacent,” she said. “Be prepared to speak out.”

Zach Wichter is a travel reporter for USA TODAY based in New York. You can reach him at zwichter@usatoday.com.

This article originally appeared on USA TODAY: She knew something was wrong when he sat near her kids. He was removed from the flight.