Los Angeles, California - A man suspected of helping another man bomb a fertility clinic in California has died in custody, officials said Tuesday.

Daniel Park (32) was accused of shipping bomb-making material to Guy Edward Bartkus (25), who died in the May 17 explosion of a car outside the clinic in Palm Springs, a desert town east of Los Angeles.

Four other people were wounded in the blast, which caused major damage to the building.

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No cause of death for Park was provided.

Authorities say he and Bartkus met online and shared "pro-mortalist, anti-natalist" beliefs.

Bartkus believed "that individuals should not be born without their consent and that non-existence is best," the Justice Department said in a statement earlier this month. Park shared this ideology.

After the attack, Park fled to Europe but was arrested in Poland at the request of the US and deported back home to face terrorism-related charges.

Since his arrest this month, Park was being held in federal custody, and on Tuesday, he was "found unresponsive" in a cell at a detention facility in Los Angeles, the Federal Bureau of Prisons said in a statement.

Officers tried to revive him, but Park was later pronounced dead at a hospital.

He was accused of shipping approximately 180 pounds of ammonium nitrate, which is used to make homemade bombs, to Bartkus.

Authorities have said Park, who lived in Seattle, and Bartkus were together in the latter's hometown of Twentynine Palms in January and February and ran bomb experiments.