Authorities say the suspect, Guy Edward Bartkus of Twentynine Palms, is the same person who was found near a charred-out vehicle by the clinic.

Akil Davis, the head of the FBI’s Los Angeles field office, said during a news conference that investigators were reviewing writings left behind by Bartkus that could shed light on his state of mind.

His writings were “anti pro-life” in nature, according to a social media post from Bilal Essayli, the US attorney in Los Angeles.

The Associated Press reported Saturday night that those writings communicated a belief that the world should not be populated.

“The subject had nihilistic ideations and this was a targeted attack against the IVF facility,” Davis said.

“Make no mistake: we are treating this, as I said yesterday, as an intentional act of terrorism.”

The bombing injured four other people in addition to killing Bartkus, though Davis said all embryos at the facility were saved.

“Good guys one, bad guys zero,” he said.

The explosion is “probably the largest bombing scene that we’ve had in Southern California,” Davis added.

Authorities were executing a search warrant in Twentynine Palms as part of the investigation.

The suspect posted writings online and attempted to record the explosion, though authorities said the video failed to upload.

An official who was not authorised to discuss details of the attack spoke on condition of anonymity to The Associated Press.

The blast gutted the single-story American Reproductive Centers clinic in upscale Palm Springs, though a doctor told the Associated Press its staff members were safe.

“Thank God today happened to be a day that we have no patients,” Dr Maher Abdallah, who leads the clinic, told the AP in a phone interview.