An explosion tore through a fertility clinic in the upscale California city of Palm Springs late Saturday morning, leaving one person believed to be the suspect dead in an attack the FBI characterized as terrorism.

A burned-out vehicle was seen in the parking lot behind the clinic after the blast, which caved in the building's roof, sprayed debris across a five-lane road and shattered windows in businesses blocks away. The clinic was closed for the weekend, and the doctor who leads it told The Associated Press its staffers were safe.

“Make no mistake: This is an intentional act of terrorism,” Akil Davis, the head of the FBI’s Los Angeles field office, told an evening news conference. He declined to say how authorities reached that conclusion.

A law enforcement official said investigators recovered an AK-47-style rifle from the scene. The official was not authorized to discuss details of the investigation publicly and spoke to the AP on condition of anonymity.

Authorities were still working to confirm the identity of the person killed, Davis said. Four people were hurt, but authorities provided no details on the severity of those injuries, how they occurred or where. Davis said law enforcement was also looking into the possibility that the explosion was livestreamed.

IN CASE YOU MISSED IT | Pakistani man faces new terrorism charge in plot to assassinate a US politician

The act was being investigated as a possible car explosion, according to two other law enforcement officials briefed on the matter who insisted on anonymity to discuss preliminary information from an ongoing investigation.

One of the officials told AP that investigators believe the person who died was likely the person who set off the explosion, but they cautioned that the investigation was still in its early stages.

The blast gutted the American Reproductive Centers fertility clinic, in a single-story building along a five-lane street lined with palm trees. Dr. Maher Abdallah, who leads the clinic, told AP in a phone interview that the explosion damaged the practice’s office space, where it conducts consultations with patients. The clinic's IVF lab and stored embryos are offsite and were not damaged.

“Thank God today happened to be a day that we have no patients," Abdallah said.

Palm Springs Mayor Pro Tem Naomi Soto called the clinic “a place of hope.”

“This is a building that people go to to start or expand their families,” she said. “We acknowledge their pain and concern across the community for the patients and staff."

Rhino Williams, 47, said he was chatting with customers at a hotel restaurant he helps manage just over a block away when he heard a huge boom. Everything rattled, Williams said, and he sprinted to the scene to see if anyone needed help.

Williams covered his nose with his shirt as he smelled burning plastic and rubber. He said he saw a building had “blown out” into the street, with bricks and debris scattered everywhere, and he spotted a car’s front axle on fire in the parking lot.

He said it was the only car in the lot. He ran into the building, calling out and peering behind the counter to see if anyone was inside. He did not hear a response and did not see anyone behind the counter.

Williams then ran around to check on other buildings. Multiple windows of the neighboring liquor store were also blown out, he said. Once he saw authorities arrive, he headed back to the hotel.

Steven Michael Chacon was in his car preparing to turn into a hospital across the street from the clinic when felt and heard a massive boom as the building was torn apart, sending a massive plume of black smoke into the air. Not knowing what happened, he exited his car to flee the scene. Glass was all over the ground.

“I got out of my car and then people started screaming, there were people bloody, there was glass everywhere,” he said.

Palm Springs, about a two-hour drive east of Los Angeles, is known for upscale resorts, golf courses and a history of celebrity residents.

Among those investigating were investigators, bomb technicians and an evidence response team from the FBI as well as investigators from the Bureau of Alcohol, Tobacco, Firearms and Explosives.

The Trump administration condemned the attack.

“The Trump administration understands that women and mothers are the heartbeat of America,” Attorney General Pam Bondi said in a statement. “Violence against a fertility clinic is unforgivable.”