(WASHINGTON) — An unidentified man entered National Security Adviser Jake Sullivan’s Washington, D.C., home in late April, prompting a Secret Service investigation, according to an agency spokesperson.

“Secret Service is examining a security incident that took place at a protectee site,” Anthony Guglielmi, the Secret Service’s director of communications, said in a statement to ABC News.

“While the protectee was unharmed, we are taking this matter seriously and have opened a comprehensive mission assurance investigation to review all facets of what occurred,” Guglielmi said. “Any deviation from our protective protocols is unacceptable and if discovered, personnel will be held accountable. Modifications to the protective posture have also been made to ensure additional security layers are in place as we conduct this comprehensive review.”

A source familiar with the incident told ABC News that the man was intoxicated and didn’t know exactly where he was, and it appears that he didn’t know he was in the home of the national security adviser.

Sullivan, like most high-profile executive branch members, has an around-the-clock Secret Service detail that monitors outside of his Washington, D.C. residence.

The incident was first reported by the Washington Post.

This is a developing story. Please check back for updates.

Copyright © 2023, ABC Audio. All rights reserved.