Los Angeles, California - An American man who believes human life should not exist has been arrested in connection with the bombing of a fertility clinic in California that killed the attacker, the FBI said Wednesday.

Daniel Park (32) was taken into custody at a New York area airport, where he arrived from Poland, on charges that he shipped explosives to the man who blew himself up in Palm Springs last month.

The explosion ripped a hole in the clinic and blew out the windows and doors of nearby buildings.

Bomber Guy Edward Bartkus (25) of the town of Twentynine Palms in California, died in the blast, which also wounded four people.

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None of the embryos stored at the clinic were affected.

US Attorney Bill Essayli said investigators probing the bombing had discovered Bartkus had "pro-mortalist, anti-natalist, and anti-pro-life extremist ideology."

Bartkus believed "that individuals should not be born without their consent and that non-existence is best," the US Justice Department said in a statement.

Essayli said Park shared those beliefs, and is accused of "shipping approximately 180 pounds of ammonium nitrate, an explosive precursor commonly used to construct homemade bombs, to Bartkus."

He said Park, who lives in Seattle, Washington, and Bartkus were together in Twentynine Palms in January and February, where they ran experiments.

Days after the attack, Park – a US citizen – fled to Poland, where he was ultimately detained by Polish law enforcement at the request of the FBI.

Park was expected to appear in court in New York on Wednesday for a hearing to determine if he can be extradited to California.

Akil Davis of the FBI said law enforcement was aware of a small nihilist movement in the US, and had been tracking it for several years, although these two men were not on their radar.

"They don't believe that people should exist," he told reporters. "There's tons of terminology out there, anti-natalism, pro-mortalism, nihilism. These all are intertwined to create their belief system."

US Attorney General Pam Bondi said the bomb attack had been a "cruel, disgusting crime that strikes at the very heart of our shared humanity."

"We are grateful to our partners in Poland who helped get this man back to America and we will prosecute him to the fullest extent of the law," she wrote on social media.