Rescue crews tend to the injured in the intersection outside the Inland Regional Center in San Bernardino, California in this still image taken from video December 2, 2015. REUTERS/NBCLA.com/Handout via Reuters

LOS ANGELES (Reuters) – Three people were killed and as many 20 were wounded on Wednesday when at least one person opened fire at a social services agency in the Southern California city of San Bernardino, authorities and a witness said.

MSNBC reported that law enforcement authorities confirmed the three deaths, and a reporter for the local NBC affiliate said he saw three bodies following the shooting rampage.

The San Bernardino Police Department said on Twitter that it had “confirmed 1 to 3 possible suspects” and multiple victims in the shooting. The agency called it an “active shooter” incident.

The San Bernardino Fire Department said in a tweet that it was responding to reports of 20 victims. San Bernardino is some 60 miles (100 km) east of Los Angeles.

A police spokeswoman told the Los Angeles Times that the suspects were heavily armed and possibly wearing body armor, and CBS reported that a bomb squad was on the scene, trying to defuse what was believed to be an explosive device.

President Barack Obama was briefed and Democratic presidential candidate Hillary Clinton said on Twitter, “I refuse to accept this as normal. We must take action to stop gun violence now.”

A spokeswoman for the Los Angeles Field Office of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives said agents were heading to the scene.

The shooting took place at the Inland Regional Center, one of 21 facilities serving people with developmental disabilities run by the state, said Nancy Lungren, spokeswoman for the California Department of Developmental Services.

Television images on CNN showed people being evacuated from the building, their arms raised, as triage stations were set up outside. Police and SWAT teams were seen surrounding the building.

Rescue crews tend to the injured in the intersection outside the Inland Regional Center in San Bernardino, California in this still image taken from video December 2, 2015. REUTERS/NBCLA.com/Handout via Reuters
Rescue crews tend to the injured in the intersection outside the Inland Regional Center in San Bernardino, California in this still image taken from video December 2, 2015. REUTERS/NBCLA.com/Handout via Reuters

HOSPITAL READIES FOR PATIENTS

A spokeswoman from nearby Loma Linda Medical Center said the hospital was expecting patients momentarily. “We’re all kind of on standby right now – it could be any minute,” spokeswoman Briana Pastorino said

The social services agency is among regional centers throughout California that administer, authorize and pay for assistance to people with disabilities such as autism and mental retardation.

On an average day, doctors at the regional centers would be evaluating toddlers whose parents have concerns and case workers meeting with developmentally disabled adults. Lungren said that the San Bernardino facility is one of the state’s largest and busiest.

The shooting in California comes less than a week after a gunman killed three people and wounded nine in a shooting rampage at a Planned Parenthood clinic in Colorado Springs. In October, a gunman killed nine people at a college in Oregon and in June a white gunman killed nine black churchgoers in South Carolina.