A Rutgers University professor known for his research on anti-fascist movements was prevented from leaving the United States for Spain on Wednesday night, hours after President Donald Trump hosted a White House event condemning antifa and its supporters.

Mark Bray, a historian and author of Antifa: The Anti-Fascist Handbook (2017), was reportedly stopped at Newark Liberty International Airport as he and his family were preparing to board a flight to Europe. According to Bray, airline staff told him that his family’s reservation had been suddenly canceled despite having boarding passes and clearing security.

Bray, who has taught anti-fascism courses at Rutgers University in New Jersey, wrote on social media: “Someone canceled my family’s flight out of the country at the last second. We got our boarding passes. We checked our bags. Went through security. Then at our gate our reservation ‘disappeared.’” He said the family has since been rebooked for another flight and is unsure why the initial booking was voided.

The professor—mockingly dubbed “Dr. Antifa” by some students—said he decided to move abroad after receiving death threats, including one threatening to kill him “in front of his students.” His home address was reportedly leaked online following the assassination of Turning Point USA founder Charlie Kirk, after which right-wing activists, including influencer Jack Posobiec, labeled him a “domestic terrorist professor.”

A petition circulated by the Rutgers chapter of Turning Point USA accused Bray of being an “antifa member” and demanded his dismissal, despite no evidence linking him to any militant activity. The group later clarified it does not endorse harassment or doxxing, though its social media post described antifa as “a designated domestic terrorist organization” and encouraged students to report him.

In response, Bray told The New York Times that he has never been affiliated with any antifa organization. “There’s an effort underway to paint me as someone who is doing the things I’ve researched, but that couldn’t be further from the truth,” he said.

In an email to students earlier this week, Bray explained his decision to relocate temporarily to Spain with his wife and two children, saying he would continue teaching remotely. “Since my family and I do not feel safe in our home at the moment, we are moving for the year to Europe,” he wrote.

Rutgers University issued a brief statement saying it does not comment on personnel matters but reaffirmed its commitment to “providing a secure environment to learn, teach, and research where all members of our community can share their opinions without fear of intimidation or harassment.”