(AP) -- One or more gunmen opened fire Wednesday at a Southern California social services center, shooting several people as others locked themselves in their offices and took cover, desperately waiting to be rescued by police, witnesses and authorities said.

Federal and local law enforcement authorities converged on the center and searched for the shooter or shooters. 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.

Triage units were set up out the Inland Regional Center, which serves people with developmental disabilities, 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.

The shooting -- less than three weeks after the Paris attacks that left 130 people dead -- immediately raised the specter of terrorism, especially after the San Bernardino police said there may have been more than one gunman, and President Barack Obama was briefed on the situation by his homeland security adviser.

But police shed no immediate light on a motive.

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.

The president and CEO of the social services center, Maybeth Feild, said the focus was on a building that houses at least 25 employees as well as a library and conference center.