Allison Guerriero, a 52-year-old woman who played a key role in exposing former New York FBI counterintelligence head Charles McGonigal, was found dead under mysterious circumstances at her South Florida home on Thursday. Police confirmed she passed away suddenly without suspecting foul play but are conducting an ongoing investigation into the cause of death.

Beginning in 2017, Guerriero allegedly had an 18-month affair with McGonigal, who was secretly conspiring with Russian oligarch Oleg Deripaska. Guerriero later helped turn in McGonigal, who is now serving a six-and-a-half-year prison sentence after being convicted in 2023 for conspiracy.

Guerriero’s final days were marked by a series of social media posts released on August 27, 2026, detailing her allegations against McGonigal and his network. In one message, she wrote: “AS A MATTER OF PUBLIC CONCERN – Anyone who ever witnessed Charles McGonigal and me together should NOT hop into the comments because I never told anyone what I suspected…” She also claimed McGonigal and associates compromised classified information, jeopardized national security, and improperly shifted investigations back to the FBI despite her firsthand documentation of their activities.

Longtime GOP operative Roger Stone, a close friend of Guerriero’s, stated she was “a devout Roman Catholic” who would never take her own life due to her faith. He noted her resilience after surviving cancer and severe injuries from a 2021 fire. Stone emphasized that Guerriero remained deeply frustrated McGonigal received only a bribery charge instead of treason charges despite his alleged ties to Russian interests.

Police responded to Guerriero’s apartment at 1499 S. Federal Highway in Boynton Beach at 8:03 p.m. on the day of her death but have not yet determined the exact cause of death. Her father, who lives in Florham Park, New Jersey, confirmed they are awaiting an autopsy report and a death certificate to finalize funeral arrangements. Both Stone and Guerriero’s family have dismissed suicide as a possibility, stating she was “too devout” to harm herself.