SAN BERNARDINO, Calif. (AP) — One or more gunmen believed to be wearing military-style gear opened fire Wednesday at a Southern California social services center, killing an undisclosed number of people and wounding several others, authorities said.

FBI agents and other law enforcement authorities converged on the center and searched for the shooter or shooters.

San Bernardino police spokesman Sgt. Vicki Cervantes told KCBS-TV that there were multiple injuries and “some confirmed fatalities,” but “I don’t have numbers at this point.”

She also said that it “appears there is more than one shooter,” and that they were believed be wearing military-style gear.

Police shed no light on a motive. President Barack Obama was briefed on the attack by his homeland security adviser.

Witnesses said several people locked themselves in their offices, desperately waiting to be rescued by police, after gunfire erupted at the Inland Regional Center, which serves people with developmental disabilities.

The attack took place in a conference area where the San Bernardino County Department of Public Health was holding a meeting, said Maybeth Field, president and CEO of the social services center. She said the building houses at least 25 employees as well as a library and conference center.

As the manhunt went on, stores, office buildings and at least one school were locked down in the city of 214,000 people about 60 miles east of Los Angeles, and roads were blocked off.

Triage units were set up outside, and people were seen being wheeled away on stretchers. Others walked quickly from a building with their hands up. They were searched by police before being reunited with loved ones.

Terry Petit said his daughter works at the center, and he got a text from her saying she was hiding in the building after hearing gunshots. Petit choked back tears as he read the texts for reporters outside the center. He said she wrote: “People shot. In the office waiting for cops. Pray for us. I am locked in an office.”

Marcos Aguilera’s wife was in the building when the gunfire erupted. He said a shooter entered the building next to his wife’s office and opened fire.

“They locked themselves in her office. They seen bodies on the floor,” Aguilera told KABC-TV, adding that his wife was able to get out of the building unharmed.

Loma Linda University Medical Center received four patients in its trauma center and expected three more, spokeswoman Briana Pastorino said. She did not know their conditions.