Federal agents arrested Daniel Park for providing chemicals used in the Palm Springs fertility clinic bombing.
They say Park, 32, purchased ammonium nitrate over several years and shipped it to the bomber, Guy Edward Bartkus.
Park fled to Poland four days after the explosion and returned this week, where authorities arrested him at JFK Airport.
He appeared in a federal court in Brooklyn on Wednesday after his extradition to the United States.
Investigators Reveal Months of Bomb-Making Activity
The FBI says Park visited Bartkus months before the May 17 attack to test explosives in a garage.
Agents say the two met in online anti-natalist forums and shared a belief that humans should not reproduce.
They reportedly conducted experiments in Bartkus’ room and garage in Twentynine Palms, California.
Park shipped 180 pounds of ammonium nitrate in January and another 90 pounds just days before the bombing.
Officials say Park started buying the explosive chemical in October 2022 and continued through May 2025.
Anti-Natalist Ideology Tied to Targeted Violence
Authorities believe Bartkus deliberately targeted the American Reproductive Centres for ideological reasons.
He died during the explosion, which damaged the clinic and nearby buildings and shattered multiple windows.
Investigators consider the incident an act of terrorism based on its ideological motive.
The FBI says Bartkus tried to livestream the blast but failed.
Officials still don’t know if he planned to die in the explosion.
FBI Finds Bomb-Making Guide at Park’s Home
Agents searched Park’s home in Kent, Washington, and discovered an explosives manual similar to Oklahoma City plans.
The FBI believes Park tried to spread anti-natalist ideology online for years.
Court records show Park posted frequently in related forums as early as 2016.
In March, he attempted to organize in-person meetings with anti-natalists in Washington.
No one responded to his call for protests or group events, officials noted.